# In situ
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{{short description|Latin phrase that translates literally to 'on site'}}
{{for|the company|Insitu, Inc.}}
{{Use dmy dates|date=October 2019}}
{{Use American English|date=February 2025}}
{{italic title}}
'''{{Lang|la|In situ}}'''{{efn|{{IPAc-en|UK|ɪ|n|_|ˈ|s|ɪ|tj|uː|audio=LL-Q1860 (eng)-Vealhurl-in situ.wav}}, {{IPAc-en|ɪ|n|_|ˈ|s|ɪ|tʃ|uː}}; {{IPAc-en|US|ˌ|ɪ|n|_|ˈ|s|aɪ|tj|uː}}, {{IPAc-en|ˌ|ɪ|n|_|ˈ|s|ɪ|tj|uː}};[{{Cite OED|In situ|9767278689}}] often not italicized in English[{{citation|year=2010|title=The Publication Manual of the American Psychological Association|edition=6th|location=Washington, DC, US|publisher=[American Psychological Association](/source/American_Psychological_Association)|isbn=978-1-4338-0562-2|section=4.21 Use of Italics}}]}} is a [Latin](/source/Latin) phrase meaning 'in the place' or 'on site', derived from ''{{linktext|in|lang=la}}'' ('in') and ''{{linktext|situ|lang=la}}'' ([ablative](/source/ablative_case) of ''situs'', {{literal|place}}).[{{cite encyclopedia | title = sĭtus | encyclopedia = A Latin Dictionary | editor-last = Lewis | editor-first = Charlton T. |editor-link=Charlton Thomas Lewis | editor2-last = Short | editor2-first = Charles | publisher = [Clarendon Press](/source/Clarendon_Press) |year = 1879 | url = https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0059%3Aentry%3Dsitus2 |via=[Perseus Digital Library](/source/Perseus_Digital_Library) |archive-url=https://web.archive.org/web/20240903151600/https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0059%3Aentry%3Dsitus2 | access-date = 11 March 2025 |archive-date=3 September 2024 |url-status=live }}] The term refers to studying or working with something in its natural or original location rather than moving it elsewhere. This approach preserves environmental factors and relationships that might be lost when [material](/source/material)s or [specimens](/source/Biological_specimen) are relocated to controlled settings. In comparison, ''{{Linktext|ex situ}}'' ('out of the place') methods involve removing materials or specimens for study, preservation, or modification under controlled conditions, often at the expense of their original context. The earliest recorded use of ''in situ'' in English dates back to the mid-17th century. Its use in [scientific literature](/source/scientific_literature) expanded from the late 19th century onward, beginning in medicine and engineering, and later spreading to a wide range of disciplines.
The [natural science](/source/natural_science)s typically use {{Lang|la|in situ}} methods to study [phenomena](/source/phenomena) in their original context. In [geology](/source/geology), field studies of [soil](/source/soil) composition and [rock formation](/source/Formation_of_rocks)s may provide direct insights into Earth's processes. Biologists observe organisms in their natural [habitat](/source/habitat)s to understand behaviors and ecological interactions that cannot be reproduced in a laboratory. In [chemistry](/source/chemistry) and [experimental physics](/source/experimental_physics), {{Lang|la|in situ}} techniques make it possible to watch substances and [reaction](/source/Chemical_reaction)s as they occur, capturing transient phenomena in real time.
The scope of these methodologies extends into [applied science](/source/applied_science)s and the [humanities](/source/humanities). In [aerospace engineering](/source/aerospace_engineering), ''in situ'' inspections and monitoring systems evaluate performance without interrupting operations. Environmental scientists use [ecosystem monitoring](/source/ecosystem_monitoring) in the field to gather reliable data with minimal disturbance. In medicine, especially [oncology](/source/oncology), ''[carcinoma in situ](/source/carcinoma_in_situ)'' describes early-stage cancers that remain localized at their site of origin. [Space exploration](/source/Space_exploration) relies on ''in situ'' methods to conduct direct observational studies and data collection on [celestial bodies](/source/celestial_bodies), avoiding the challenges of [sample-return mission](/source/sample-return_mission)s. In [archaeology](/source/archaeology), {{Lang|la|in situ}} generally refers to [artifacts](/source/Artifact_(archaeology)) and features found in undisturbed depositional settings, where recording spatial and [stratigraphic](/source/Stratigraphy_(archaeology)) relationships preserves information about past human activities. In art, {{Lang|la|in situ}} refers to works created or displayed in dialogue with their surroundings: [site-specific project](/source/Site-specific_art)s, such as [environmental sculpture](/source/environmental_sculpture)s or architectural installations, are conceived for particular locations.
==History==
[[File:Page 63 of the 1648 anatomical text Myskotomia.jpg|thumb|William Molins' ''Myskotomia'' (1648), showing the term ''in situ'' in an anatomical context.{{efn|[Diplomatic transcription](/source/Diplomatic_transcription) (original spelling) of the passage:{{quote|[…] To finde ''Sacer'' (not dissected afore this Body) you must raise ''[Dorsi Longissimus](/source/longissimus)'' and ''[Sacrolumbus](/source/Iliocostalis)'' from their membranous origination at ''Os Ileon'', ''Os Sacrum'', and from the ''Spines'' of the ''[Lumbi](/source/lumbar_vertebrae)'', and immediately under that, will appear this in ''Situ'', and in clearing him well, you will remove the scruple some make of the origination of ''[Semispinatus](/source/Semispinalis_muscles)'' and ''[Spinatus](/source/Spinalis)'', one beginning where the other ends.}}{{align|right|— ''Myskotomia'' (1648), page 63}}{{clear}}}} The ''[Oxford English Dictionary](/source/Oxford_English_Dictionary)'' cites this as the earliest known use of the phrase in English.[]]
The term ''in situ'' does not appear in [Classical Latin](/source/Classical_Latin). Its earliest recorded use is in [Late Latin](/source/Late_Latin), with the first known instance in the writings of [Augustine of Hippo](/source/Augustine_of_Hippo) (354–430{{nbsp}}AD).][{{rp|page=1536}}{{efn|An example of Augustine's use of the expression appears in {{lang|la|Contra secundam Iuliani responsionem imperfectum opus}} ('Unfinished Work Against Julian's Second Reply'), {{lang|la|Liber Quintus}} ('Book Five'): {{quote|{{lang|la|Utque ad causam referatur exemplum; naturae humanae generalitas institutionum infra se locatarum genus quoddam est; haec velut species habet, in situ, in membris, in ordinibus, in motibus, vel aliis id genus.}}][{{cite book
|author=Augustine of Hippo
|author-link=Augustine of Hippo
|title=Contra secundam Iuliani responsionem imperfectum opus
|trans-title=Unfinished Work Against Julian's Second Reply
|chapter=Liber Quintus
|series=[Patrologia Latina](/source/Patrologia_Latina)
|volume=45
|publisher=[Jacques Paul Migne](/source/Jacques_Paul_Migne)
|lang=la
|chapter-url=https://www.augustinus.it/latino/incompiuta_giuliano/incompiuta_giuliano_5_libro.htm
|access-date=9 October 2025
|via=www.augustinus.it
}}]}}}} It became widely used in [Medieval Latin](/source/Medieval_Latin).[{{rp|page=1536}} In English, the earliest known usage dates to the mid-17th century; the ''[Oxford English Dictionary](/source/Oxford_English_Dictionary)'' cites the first appearance in 1648, in William Molins' anatomical text ''Myskotomia''.][ The usages in [scientific literature](/source/scientific_literature) increased from the late 19th century onward, initially in medicine and engineering, including [geological survey](/source/geological_survey)s and [petroleum extraction](/source/extraction_of_petroleum). During this period, the term described analyses conducted within the living human body or inside [oil well](/source/oil_well)s, among other applications.][{{rp|page=1534}} ''In situ'' entered French medical discourse by 1877 in the {{lang|fr|Journal de médecine et de chirurgie pratiques}} ('Journal of Practical Medicine and Surgery').][{{Cite web|url=https://stella.atilf.fr/Dendien/scripts/tlfiv5/advanced.exe?8;s=2172540075; |title=in situ |website=[Trésor de la langue française informatisé](/source/Tr%C3%A9sor_de_la_langue_fran%C3%A7aise_informatis%C3%A9) |publisher=ATILF – Analyse et traitement informatique de la langue française |access-date=18 April 2025 |lang=fr }}] The [compound](/source/Compound_(linguistics)) term ''[carcinoma in situ](/source/carcinoma_in%26nbsp%3Bsitu)'', referring to abnormal [cells](/source/cell_(biology)) that confined to their original location without [invasion](/source/Invasion_(cancer)) of surrounding [tissue](/source/tissue_(biology)), was first used in a 1932 paper by U.S. surgical pathologist [Albert C. Broders](/source/Albert_C._Broders).[{{Cite OED|carcinoma in situ|1023159588}}][{{cite journal |last=Wright |first=James R. Jr. |title=Albert C. Broders' paradigm shifts involving the prognostication and definition of cancer |journal=[Archives of Pathology & Laboratory Medicine](/source/Archives_of_Pathology_%26_Laboratory_Medicine) |date=2012 |volume=136 |issue=11 |pages=1437–1446 |doi=10.5858/arpa.2011-0567-HP |pmid=23106590 }}]
The concept of ''in situ'' in [contemporary art](/source/contemporary_art) developed in the late 1960s and 1970s as a framework for artworks created specifically for a given space.[{{cite journal |last1=Peterson |first1=Vanessa K. |author-link=Vanessa Peterson |last2=Bianchini |first2=Matteo |last3=Chapman |first3=Karena W. |author-link3=Karena Chapman |last4=Elice |first4=Martina |last5=Hibbert |first5=David Brynn |title=Terms of Latin origin relating to sample characterization (IUPAC Technical Report) |journal=[Pure and Applied Chemistry](/source/Pure_and_Applied_Chemistry) |date=2024 |volume=96 |issue=11 |pages=1531–1540 |doi=10.1515/pac-2022-1103 |doi-access=free |publisher=[De Gruyter](/source/De_Gruyter)|hdl=11577/3522161 |hdl-access=free }}]{{rp|page=1534}} {{As of|August 2022}}, the term ''in{{nbsp}}situ'' had been used in more than 910,000 scientific publications since 1874, while ''{{linktext|ex situ}}'' had appeared in over 29,000 scientific publications since 1958.[{{rp|page=1535}}
==Applications==
===Natural sciences===
====Astronomy====
In [astronomy](/source/astronomy), ''in situ'' measurement involves collecting data directly at or near a [celestial object](/source/celestial_object) using spacecraft or instruments physically present at the location.][{{cite book |last=Casoli |first=Fabienne |author-link=Fabienne Casoli |editor-last=Lasota |editor-first=Jean-Pierre |chapter=10. The Future of Space Astronomy |title=Astronomy at the Frontiers of Science |publisher=[Springer Netherlands](/source/Springer_Netherlands) |year=2011 |pages=175–176 |isbn=978-94-007-1658-2 |url=https://books.google.com/books?id=XGwTsKteQAkC |via=[Google Books](/source/Google_Books) |access-date=23 February 2025}}] For example, the [Parker Solar Probe](/source/Parker_Solar_Probe) conducts ''in situ'' studies of [Sun's atmosphere](/source/Sun's_atmosphere),[{{cite journal |last=Phan |first=T. D. |author2=Bale, S. D. |author3=Eastwood, J. P. |author4=Larson, D. E. |author5=MacDowall, R. J. |author6=Pulupa, M. |author7=Whittlesey, P. |author8=Mozer, F. S. |author9=Drake, J. F. |author10=Oieroset, M. |author11=Shay, M. A. |author12=Haggerty, C. C. |author13=Halekas, J. S. |author14=McManus, M. D. |author15=Verniero, J. L. |author16=Case, A. W. |author17=Kasper, J. C. |author18=Korreck, K. E. |author19=Stevens, M. L. |author20=Szabo, A. |author21=MacDowall, R. J. |author22=Malaspina, D. M. |author23=Bonnell, J. W. |author24=Dudok de Wit, T. |author25=Goetz, K. |author26=Harvey, P. R. |author27=Horbury, T. S. |author28=Livi, R. |author29=Paulson, K. |author30=Raouafi, N. E. |author31=Velli, M. |title=Parker Solar Probe In Situ Observations of Magnetic Reconnection Exhausts during Encounter 1 |journal=The Astrophysical Journal Supplement Series |volume=246 |issue=2 |page=34 |date=February 2020 |doi=10.3847/1538-4365/ab55ee |doi-access=free |arxiv=2001.06048 |bibcode=2020ApJS..246...34P}}] while the ''[Cassini–Huygens](/source/Cassini%E2%80%93Huygens)'' mission similarly analyzed [Saturn](/source/Saturn)'s [magnetosphere](/source/magnetosphere).[{{cite web |title=Cassini Orbiter |url=https://science.nasa.gov/mission/cassini/spacecraft/cassini-orbiter/ |quote=The fields and particles instruments took "in situ" (on site) direct sensing measurements [...] |website=NASA Science |date=21 August 2018 |publisher=[NASA](/source/NASA) |access-date=23 February 2025 |archive-date=16 February 2025 |archive-url=https://web.archive.org/web/20250216153855/https://science.nasa.gov/mission/cassini/spacecraft/cassini-orbiter/ |url-status=live }}] ''In situ'' formation refers to astronomical objects that formed at their current locations without significant migration. Some theories propose that planets, such as Earth, formed in their present orbits rather than moving from elsewhere. [Star cluster](/source/Star_cluster)s may form within their [host galaxy](/source/host_galaxy), rather than being accreted from external sources.[{{cite journal |last1=Chiang |first1=Eugene |last2=Laughlin |first2=Gregory P. |author-link2=Gregory P. Laughlin |title=The minimum-mass extrasolar nebula: in situ formation of close-in super-Earths |journal=Monthly Notices of the Royal Astronomical Society |date=June 2013 |volume=431 |issue=4 |pages=3444–3455 |doi=10.1093/mnras/stt424 |doi-access=free |bibcode=2013MNRAS.431.3444C |arxiv=1211.1673 }}][{{cite journal |last1=D'Angelo |first1=Gennaro |last2=Bodenheimer |first2=Peter |title=In Situ and Ex Situ Formation Models of Kepler 11 Planets |journal=The Astrophysical Journal |date=September 2016 |volume=828 |issue=1 |page=33 |doi=10.3847/0004-637X/828/1/33 |doi-access=free |arxiv=1606.08088 |bibcode=2016ApJ...828...33D }}]
====Biology====
{{Further|In situ hybridization}}
[[File:HCR-FISH visualization of collagen expression in P. waltl.jpg|thumb|upright=0.9|[Gene expression](/source/Gene_expression) of [collagen](/source/collagen) in [Iberian ribbed newt](/source/Iberian_ribbed_newt), via Hybridization Chain Reaction RNA Fluorescence ''In Situ'' Hybridization]]
In [cell biology](/source/cell_biology), ''in situ'' techniques allow the examination of [cells](/source/cell_(biology)) or [tissues](/source/tissue_(biology)) within their native environment, preserving their natural structure and context. These approaches contrast with techniques requiring the extraction or isolation of cellular components. One example is [''in situ'' hybridization](/source/in_situ_hybridization) (ISH), a technique designed to identify and localize specific [nucleic acid sequence](/source/nucleic_acid_sequence)s within intact cells or tissue sections. {{Abbr|ISH|''In situ'' hybridization}} employs labeled probes, which are strands of [nucleic acid](/source/nucleic_acid)s engineered to bind selectively to target sequences. These probes are tagged with detectable markers, such as [fluorophore](/source/fluorophore)s or [radioactive isotope](/source/radioactive_isotope)s, enabling visualization of the precise spatial distribution of the targeted [DNA](/source/DNA) or [RNA](/source/RNA). By maintaining the structural integrity of the sample, the technique facilitates mapping of genetic material within its original cellular or tissue framework.[{{cite journal |last=Jensen |first=Ellen |title=Technical Review: In Situ Hybridization |journal=[The Anatomical Record](/source/The_Anatomical_Record) |volume=297 |issue=8 |pages=1349–1353 |date=August 2014 |doi=10.1002/ar.22944|pmid=24810158 }}][{{cite book |last1=Lehmann |first1=Ruth |last2=Tautz |first2=Diethard |title=''In Situ'' Hybridization to RNA |series=Methods in Cell Biology |date=1994 |volume=44 |pages=575–598 |doi=10.1016/s0091-679x(08)60933-4 |pmid=7535885 |isbn=978-0-12-564145-6 }}]
In biological [field research](/source/field_research), the term ''in situ'' refers to the study of living [organism](/source/organism)s within their natural [habitat](/source/habitat). This includes collecting biological samples, conducting experiments, measuring abiotic factors, and documenting [ecological](/source/ecological) or behavioral observations without relocating the subject.[{{cite journal |last1=Ramírez-Castañeda |first1=Valeria |last2=Westeen |first2=Erin P. |last3=Frederick |first3=Jeffrey |last4=Amini |first4=Sina |last5=Wait |first5=Daniel R. |last6=Achmadi |first6=Anang S. |last7=Andayani |first7=Noviar |last8=Arida |first8=Evy |title=A set of principles and practical suggestions for equitable fieldwork in biology |journal=[Proceedings of the National Academy of Sciences of the United States of America](/source/Proceedings_of_the_National_Academy_of_Sciences_of_the_United_States_of_America) |year=2022 |volume=119 |issue=34 |article-number=e2122667119 |doi=10.1073/pnas.2122667119|doi-access=free |pmid=35972961 |pmc=9407469 |bibcode=2022PNAS..11922667R }}][{{cite journal |last1=Brown |first1=Culum |last2=Jones |first2=Felicity |last3=Braithwaite |first3=Victoria A. |title=In situ examination of boldness–shyness traits in the tropical poeciliid, Brachyraphis episcopi |journal=Animal Behaviour |volume=70 |issue=5 |pages=1003–1009 |date=November 2005 |doi=10.1016/j.anbehav.2004.12.022 |bibcode=2005AnBeh..70.1003B }}]
====Chemistry====
In [organic chemistry](/source/organic_chemistry), ''in situ'' refers to processes that take place within the [reaction mixture](/source/reaction_mixture) without isolating [intermediates](/source/reaction_intermediate). In one-pot synthetic sequences, for example, ''in{{nbsp}}situ'' work-up modifications allow multiple reaction steps to proceed within a single vessel, reducing personnel exposure to unstable or hazardous substances (such as [azide](/source/azide) intermediates{{efn|[Sodium azide](/source/Sodium_azide) and its [conjugate acid](/source/conjugate_acid)—[hydrazoic acid](/source/hydrazoic_acid)—are both referred to as ''[azide](/source/azide)''.[{{cite journal |last1=Treitler |first1=Daniel S. |last2=Leung |first2=Simon |title=How Dangerous is Too Dangerous? A Perspective on Azide Chemistry |journal=The Journal of Organic Chemistry |date=2022 |volume=87 |issue=17 |pages=11293–11295 |doi=10.1021/acs.joc.2c01402 |pmid=36052475 }}] and respiratory poisons.[{{cite journal | last1=Tat | first1=John | last2=Heskett | first2=Karen | last3=Satomi | first3=Shiho | last4=Pilz | first4=Renate B. | last5=Golomb | first5=Beatrice A. | last6=Boss | first6=Gerry R. | title=Sodium azide poisoning: A narrative review |journal=[Clinical Toxicology](/source/Clinical_Toxicology) | date=2021 | volume=59 | issue=8 | pmid=34128439 | pmc=8349855 | doi=10.1080/15563650.2021.1906888 | pages=683–697}}]{{rp|page=684}}}}), which may pose safety risks if isolated.[{{cite journal|last= Hayashi | first = Yujiro |date = 2016 |title = Pot economy and one-pot synthesis |journal= [Chemical Science](/source/Chemical_Science_(journal)) | volume = 7 | issue = 2 | pages = 866–880 |doi = 10.1039/C5SC02913A | pmid = 28791118 | pmc = 5529999 }}]{{rp|page=872}} Another example is the [Corey–Chaykovsky reagent](/source/Corey%E2%80%93Chaykovsky_reagent), a sulfur [ylide](/source/ylide), is generated ''in{{nbsp}}situ'' by [deprotonating](/source/deprotonation) sulfonium [halide](/source/halide)s with a strong [base](/source/Base_(chemistry)).[{{cite web |title=Corey–Chaykovsky reaction |url=https://www.organic-chemistry.org/namedreactions/corey-chaykovsky-reaction.shtm |website=Organic Chemistry Portal |access-date=24 February 2025 |archive-url=https://web.archive.org/web/20241013015827/https://www.organic-chemistry.org/namedreactions/corey-chaykovsky-reaction.shtm |archive-date=13 October 2024 }}][{{cite journal|last1= Xiang | first1 = Y. | last2 = Fan | first2 = X. | last3 = Cai | first3 = P.-J. | last4 = Yu | first4 = Z.-X. | date = 2019 |title = Understanding regioselectivities of Corey–Chaykovsky reactions of dimethylsulfoxonium methylide (DMSOM) and dimethylsulfonium methylide (DMSM) toward enones: A DFT study |journal= [European Journal of Organic Chemistry](/source/European_Journal_of_Organic_Chemistry) | volume = 2019 | issue = 3 | pages = 582–590 |doi = 10.1002/ejoc.201801216 }}] This approach is used because unstablized sulfur ylides are highly reactive; if isolated, they may decompose or lose [reactivity](/source/Reactivity_(chemistry)). Consequently, their direct generation and use within the reaction mixture is more practical.[{{cite journal |last1=Bisag |first1=Giorgiana Denisa |last2=Ruggieri |first2=Silvia |last3=Fochi |first3=Mariafrancesca |last4=Bernardi |first4=Luca |title=Sulfoxonium ylides: Simple compounds with chameleonic reactivity |journal=Organic & Biomolecular Chemistry |date=2020 |volume=18 |issue=43 |pages=8793–8809 |doi=10.1039/D0OB01822H |pmid=33084717 |hdl=11585/787170 |hdl-access=free }}]
Analytical techniques such as [nuclear magnetic resonance](/source/nuclear_magnetic_resonance) (NMR) spectroscopy, [Raman spectroscopy](/source/Raman_spectroscopy), and [mass spectrometry](/source/mass_spectrometry) facilitate real-time monitoring of ''in{{nbsp}}situ'' reactions. These methods detect short-lived substances that form during a reaction, such as intermediates that might not be stable enough to isolate, and adjust conditions to improve the process; all without disturbing the reaction itself.[{{cite journal |title=In situ Spectroscopy: Delineating the mechanistic understanding of electrochemical energy reactions |author1-first=Jayaraman |author1-last=Theerthagiri |author2-first=K. |author2-last=Karuppasamy |author3-first=C.|author3-last=Justin Raj|author4-first=M.L.|author4-last=Aruna Kumari|author5-first=L.|author5-last=John Kennedy|author6-first=Gilberto|author6-last=Maia|author7-first=Neshanth|author7-last=Vadivel|author8-first=Arun Prasad|author8-last=Murthy|author9-first=Akram|author9-last=Alfantazi|author10-first=Soorathep|author10-last=Kheawhom |author11-first=Myong Yong |author11-last=Choi |journal=[Progress in Materials Science](/source/Progress_in_Materials_Science) |volume=152 |year=2025 |article-number=101451 |doi=10.1016/j.pmatsci.2025.101451 }}][{{cite journal| last1 = Zhang | first1 = Dongao | last2 = Liu | first2 = Xuan | last3 = Zhao | first3 = Yu | last4 = Zhang | first4 = Hua | last5 = Rudnev | first5 = Alexander V. | last6 = Li | first6 = Jian-Feng |title = In situ Raman spectroscopic studies of CO₂ reduction reactions: from catalyst surface structures to reaction mechanisms |journal = [Chemical Science](/source/Chemical_Science_(journal)) | year = 2025 | volume = 16 | issue = 12 | pages = 4916–4936 | doi = 10.1039/D5SC00569H | pmid = 40007664 | pmc = 11848642 }}][{{cite journal |last1=Buser |first1=Jonas Y. |last2=McFarland |first2=Adam D. |title=Reaction characterization by flow NMR: Quantitation and monitoring of dissolved {{chem|H|2}} via flow NMR at high pressure |journal=[Chemical Communications](/source/Chemical_Communications) |date=2014 |volume=50 |issue=32 |pages=4234–4237 |doi=10.1039/C4CC00055B |pmid=24633225 }}]
In [electrochemistry](/source/electrochemistry), ''in situ'' experiments are performed under the normal operating conditions of an [electrochemical cell](/source/electrochemical_cell), with the [electrode](/source/electrode) maintained at a controlled [potential](/source/Electrode_potential) (typically by a [potentiostat](/source/potentiostat)).[{{cite book|last1=Kolb |first1=Dieter M. | last2=Simeone | first2=Felice C. | chapter=Characterization and Modification of Electrode Surfaces by In Situ STM | title=Scanning Tunneling Microscopy in Surface Science, Nanoscience and Catalysis | editor1-last=Bowker | editor1-first=Michael | editor2-last=Davies | editor2-first=Philip R. |url=https://books.google.com/books?id=5K16aBTAmMYC |via=[Google Books](/source/Google_Books) | publisher=Wiley-VCH | year=2009 | pages=119–122 | isbn=978-3-527-31982-4 }}] By contrast, ''ex situ'' experiments occur outside those operating conditions, usually without potential control; for example, after the electrode has been removed from the cell or left at [open-circuit](/source/Open-circuit_voltage). Maintaining potential control in ''in situ'' measurements preserves the electrochemical environment at the electrode–electrolyte interface, thereby keeping the [double layer](/source/Double_layer_(surface_science)) and ongoing [electron-transfer](/source/electron-transfer) reactions intact at a given electrode potential.[{{cite journal|last1=Brummel | first1=Olaf | last2=Lykhach | first2=Yaroslava | last3=Ralaiarisoa | first3=Maryline |title=A Versatile Approach to Electrochemical In Situ Ambient-Pressure X-ray Photoelectron Spectroscopy: Application to a Complex Model Catalyst | journal=[The Journal of Physical Chemistry Letters](/source/The_Journal_of_Physical_Chemistry_Letters) | year=2022 | volume=13 | issue=47 | pages=11015–11022| doi=10.1021/acs.jpclett.2c03004 | pmid=36411106 | bibcode=2022JPCL...1311015B | hdl=11311/1229225 | hdl-access=free }}][{{cite journal| last1=Brimaud | first1=Sylvain | last2=Jusys | first2=Zenonas | last3=Behm | first3=R. Jürgen | title=Shape-selected nanocrystals for in situ spectro-electrochemistry studies on structurally well defined surfaces under controlled electrolyte transport: A combined in situ ATR-FTIR/online DEMS investigation of CO electrooxidation on Pt | journal=[Beilstein Journal of Nanotechnology](/source/Beilstein_Journal_of_Nanotechnology) | year=2014 | volume=5 | pages=735–746 | doi=10.3762/bjnano.5.86 | pmid=24991511 | pmc=4077536 }}]
===Applied sciences===
====Aerospace engineering====
{{Broader|Structural health monitoring}}
{{Further|In situ resource utilization}}
In aerospace [structural health monitoring](/source/structural_health_monitoring), ''in situ'' inspection involves diagnostic techniques that assess components within their operational environments, avoiding the need for disassembly or service interruptions. The [nondestructive testing](/source/nondestructive_testing) (NDT) methods commonly used for ''in situ'' damage detection include [infrared thermography](/source/infrared_thermography), which measures [thermal emission](/source/thermal_emission)s to identify structural anomalies but is less effective on low-[emissivity](/source/emissivity) materials;[{{cite web | url=https://www.flir.com/discover/professional-tools/how-does-emissivity-affect-thermal-imaging/?srsltid=AfmBOopyv0S_iwA3Cz9ssDWC8GJny8SnmJWj-ytZ4VzunW6git0eJ1aD |archive-url=https://web.archive.org/web/20250218180532/https://www.flir.com/discover/professional-tools/how-does-emissivity-affect-thermal-imaging/?srsltid=AfmBOopyv0S_iwA3Cz9ssDWC8GJny8SnmJWj-ytZ4VzunW6git0eJ1aD |archive-date=18 February 2025 | title=How Does Emissivity Affect Thermal Imaging? | date=1 November 2021 |access-date=2024-10-12 |publisher=[Teledyne FLIR](/source/Teledyne_FLIR) }}] speckle shearing [interferometry](/source/interferometry) ([shearography](/source/shearography)), which analyzes surface deformation patterns but requires carefully controlled environmental conditions;[{{cite book | chapter-url=https://doi.org/10.1007/978-3-319-26553-7_3 | doi=10.1007/978-3-319-26553-7_3 | chapter=Shearography | title=Handbook of Advanced Nondestructive Evaluation | date=2019 | last1=Yang | first1=Lianxiang | last2=Li | first2=Junrui | pages=383–384 | isbn=978-3-319-26552-0 }}] and [ultrasonic testing](/source/ultrasonic_testing), which uses [sound wave](/source/sound_wave)s to detect internal defects in [composite material](/source/composite_material)s but can be time-intensive for large structures.[{{cite book |last1=Rizzo |first1=P. |title=Sensor Technologies for Civil Infrastructures |chapter=Sensing solutions for assessing and monitoring underwater systems |date=2022 |pages=355–376 |doi=10.1016/B978-0-08-102706-6.00018-0 |isbn=978-0-08-102706-6 }}] Despite these individual limitations, the integration of these complementary techniques yields higher overall diagnostic accuracy.[{{cite journal |last1=Addepalli |first1=Sri |last2=Roy |first2=Rajkumar |last3=Axinte |first3=Dragoş |last4=Mehnen |first4=Jörn |title='In-situ' Inspection Technologies: Trends in Degradation Assessment and Associated Technologies |journal=Procedia CIRP |date=2017 |volume=59 |page=37 |doi=10.1016/j.procir.2016.10.003 }}]
[[File:Orion Artemis I Selfie 1.jpg|thumb|upright=0.9|Photo of Orion taken during the flight of [Artemis I](/source/Artemis_I)]]
Future [space exploration](/source/space_exploration) and [terraforming](/source/terraforming) efforts may depend on [in situ resource utilization](/source/in_situ_resource_utilization), reducing reliance on Earth-based supplies. Proposed missions, such as [Orion](/source/Orion_(spacecraft)) and [Mars Direct](/source/Mars_Direct), have explored this approach by leveraging locally available materials. The Orion space vehicle was once considered for propulsion using fuel extracted from the Moon, while Mars Direct relies on the [Sabatier reaction](/source/Sabatier_reaction) to synthesize [methane](/source/methane) and water from atmospheric [carbon dioxide](/source/carbon_dioxide) and hydrogen on Mars.[{{cite journal | last1 = Zubrin | first1 = Robert M. |author-link1=Robert Zubrin | last2 = Muscatello | first2 = Anthony C. | last3 = Berggren | first3 = Michael | title = Integrated Mars In Situ Propellant Production System | journal =[Journal of Aerospace Engineering](/source/Journal_of_Aerospace_Engineering) | volume = 26 | issue = 1 | pages = 44–56 | year = 2013 | doi = 10.1061/(ASCE)AS.1943-5525.0000201 }}][{{cite web | last = Sercel | first = Joel | author-link = Joel C. Sercel | title = Lunar Polar Propellant Mining Outpost (LPMO): A Breakthrough for Lunar Exploration & Industry | website = [NASA](/source/NASA) | date = 7 April 2020 | url = https://www.nasa.gov/general/lunar-polar-propellant-mining-outpost-lpmo-a-breakthrough-for-lunar-exploration-industry/ | access-date = 2 March 2025 | archive-date = 30 January 2025 | archive-url = https://web.archive.org/web/20250130122447/https://www.nasa.gov/general/lunar-polar-propellant-mining-outpost-lpmo-a-breakthrough-for-lunar-exploration-industry/ | url-status = live }}]
====Biological and biomedical engineering====
{{Further|In situ polymerization}}
In [biological engineering](/source/biological_engineering), ''in situ'' describes experimental treatments applied to [cells](/source/cell_(biology)) or [tissues](/source/tissue_(biology)) while they remain intact, rather than using extracts. It also refers to [assay](/source/assay)s or manipulations performed on whole tissues without disrupting their natural structure.[{{cite book |last=Goyal |first=M. R. |author-link=Megh R. Goyal |year=2018 |title=Scientific and Technical Terms in Bioengineering and Biological Engineering |publisher=Apple Academic Press, [Taylor & Francis](/source/Taylor_%26_Francis) |isbn=978-1-351-36035-7 }}]{{rp|pages=295–296}}
In [biomedical engineering](/source/biomedical_engineering), [''in situ'' polymerization](/source/in_situ_polymerization) is used to produce protein [nanogel](/source/nanogel)s, which serve as a versatile platform for the storage and release of [therapeutic protein](/source/therapeutic_protein)s. This approach has applications in [cancer treatment](/source/cancer_treatment), vaccination, diagnostics, [regenerative medicine](/source/regenerative_medicine), and therapies for loss-of-function genetic diseases.[{{cite journal|last1=Ye|first1=Yanqi|last2=Yu|first2=Jicheng|last3=Gu|first3=Zhen|year=2015|title=Versatile Protein Nanogels Prepared by In Situ Polymerization|journal=Macromolecular Chemistry and Physics|volume=217|issue=3|pages=333–343|doi=10.1002/macp.201500296}}]
====Civil engineering====
{{Further|Cast-in-place concrete}}
In [construction engineering](/source/construction_engineering), ''in situ'' construction refers to building work carried out directly on-site using [raw material](/source/raw_material)s, as opposed to [prefabrication](/source/prefabrication), where components are manufactured off-site and assembled on-site. [''In situ'' concrete](/source/Cast-in-place_concrete) is poured at its final location, offering structural stability compared to precast construction.[{{cite book |last=Collum |first=Bill |title=Nuclear Facilities: A Designer's Guide |chapter=Chapter 5. Structural |year=2016 |publisher=[Elsevier Science](/source/Elsevier_Science) |location=Netherlands |series=Woodhead Publishing Series in Energy |volume=112 |isbn=978-0-08-101939-9}}]{{rp|page=117}} Prefabrication, in contrast, reduces on-site labor requirements and shortens project timelines, but requires precise pre-planning and involves higher manufacturing and transportation costs.[{{cite journal |last1=Tavares |first1=V. |last2=Soares |first2=N. |last3=Raposo |first3=N. |last4=Marques |first4=P. |last5=Freire |first5=F. |title=Prefabricated versus conventional construction: Comparing life-cycle impacts of alternative structural materials |journal=Journal of Building Engineering |volume=41 |year=2021 |article-number=102705 |doi=10.1016/j.jobe.2021.102705}}][{{cite journal |last1=Zhang |first1=Wei |last2=Lee |first2=Ming Wai |last3=Jaillon |first3=Lara |last4=Poon |first4=Chi-Sun |title=The hindrance to using prefabrication in Hong Kong's building industry |journal=[Journal of Cleaner Production](/source/Journal_of_Cleaner_Production) |volume=204 |year=2018 |pages=70–81 |doi=10.1016/j.jclepro.2018.08.190 |bibcode=2018JCPro.204...70Z }}][{{cite journal |last1=Chen |first1=Ying |last2=Okudan |first2=Gül E. |last3=Riley |first3=David R. |title=Decision support for construction method selection in concrete buildings: Prefabrication adoption and optimization |journal=[Automation in Construction](/source/Automation_in_Construction) |volume=19 |issue=6 |year=2010 |pages=665–675 |doi=10.1016/j.autcon.2010.02.011 |bibcode=2010AutCo..19..665C }}]
In [geotechnical engineering](/source/geotechnical_engineering), the term ''in situ'' describes [soil](/source/soil) in its natural, undisturbed state,[{{cite web | author = New Zealand Geotechnical Society Inc. | editor1-last = Burns | editor1-first = David | editor2-last = Farqhuar | editor2-first = Geoffrey | editor3-last = Mills | editor3-first = Mandy | editor4-last = Williams | editor4-first = Ann | date = December 2005 | title = Field Description of Soil and Rock: Guideline for the Field Classification and Description of Soil and Rock for Engineering Purposes | url = https://www.geoengineer.org/storage/education/64/general_file_collection/17735/NZGS-2005-Field-description-of-soil-and-rock.pdf | access-date = 27 February 2025 | website = geoengineer.org | archive-date = 18 May 2024 | archive-url = https://web.archive.org/web/20240518155651/https://www.geoengineer.org/storage/education/64/general_file_collection/17735/NZGS-2005-Field-description-of-soil-and-rock.pdf | url-status = live }}]{{rp|page=15}} as opposed to [fill material](/source/fill_material), which has been excavated and relocated. The differences between undisturbed soil and fill material affect how well a site can support structures, install underground utilities, and manage [water drainage](/source/water_drainage). Proper assessment of soil conditions is necessary to prevent issues such as uneven settling, unstable [foundations](/source/Foundation_(engineering)), and poor [water infiltration](/source/water_infiltration).[{{cite encyclopedia |last1=Nimmo |first1=John R. |last2=Shillito |first2=Rose M. |title=Infiltration of Water Into Soil |encyclopedia=Oxford Research Encyclopedia of Environmental Science |date=2023 |publisher=[Oxford University Press](/source/Oxford_University_Press) |doi=10.1093/acrefore/9780199389414.013.768 |isbn=978-0-19-938941-4 }}][{{cite journal |last1=Cardarelli |first1=Ettore |last2=Cercato |first2=Michele |last3=Di Filippo |first3=Gerardina |title=Assessing foundation stability and soil-structure interaction through integrated geophysical techniques: a case history in Rome (Italy) |journal=Near Surface Geophysics |volume=5 |issue=2 |pages=141–147 |date=December 2007 |doi=10.3997/1873-0604.2006026 |bibcode=2007NSGeo...5..141C }}]
====Computer science====
{{Further|In-situ processing|In-place algorithm}}
{{seealso|In situ adaptive tabulation}}
In [computer science](/source/computer_science), ''in situ'' refers to the use of technology and [user interface](/source/user_interface)s to provide continuous access to situationally relevant information across different locations and contexts.[{{cite journal |last1=Ens |first1=Barrett |last2=Irani |first2=Pourang |title=Spatial Analytic Interfaces: Spatial User Interfaces for In Situ Visual Analytics |journal=IEEE Computer Graphics and Applications |date=March 2017 |volume=37 |issue=2 |pages=66–79 |doi=10.1109/MCG.2016.38 |pmid=28113834 |bibcode=2017ICGA...37b..66E }}][{{cite journal |last1=Willett |first1=Wesley |last2=Jansen |first2=Yvonne |last3=Dragicevic |first3=Pierre |title=Embedded Data Representations |journal=IEEE Transactions on Visualization and Computer Graphics |date=2017 |volume=23 |issue=1 |pages=461–470 |doi=10.1109/TVCG.2016.2598608 |pmid=27875162 |bibcode=2017ITVCG..23..461W |url=https://inria.hal.science/hal-01377901 }}] Examples include athletes viewing biometric data on smartwatches to improve their performance[{{cite book |doi=10.1145/3154862.3154879 |chapter=Data representations for in-situ exploration of health and fitness data |title=Proceedings of the 11th EAI International Conference on Pervasive Computing Technologies for Healthcare |date=2017 |last1=Amini |first1=Fereshteh |last2=Hasan |first2=Khalad |last3=Bunt |first3=Andrea |last4=Irani |first4=Pourang |pages=163–172 |isbn=978-1-4503-6363-1 }}] or a presenter looking at tips on a smart glass to reduce their speaking rate during a speech.[{{cite book |doi=10.1145/2678025.2701386 |chapter=Rhema: A Real-Time In-Situ Intelligent Interface to Help People with Public Speaking |title=Proceedings of the 20th International Conference on Intelligent User Interfaces |date=2015 |last1=Tanveer |first1=M. Iftekhar |last2=Lin |first2=Emy |last3=Hoque |first3=Mohammed (Ehsan) |pages=286–295 |isbn=978-1-4503-3306-1 }}]
An [algorithm](/source/algorithm) is said to be an [''in situ'' algorithm, or in-place algorithm](/source/in-place_algorithm), if the extra amount of memory required to execute the algorithm is [O(1)](/source/O(1)).[{{cite journal |last1=Munro |first1=J. Ian |last2=Raman |first2=Venkatesh |last3=Salowe |first3=Jeffrey S. |title=Stable in situ sorting and minimum data movement |journal=BIT |date=June 1990 |volume=30 |issue=2 |pages=220–234 |doi=10.1007/BF02017344 }}] With [big data](/source/big_data), in situ data would mean bringing the computation to where data is located, rather than the other way like in traditional RDBMS systems where data is moved to computational space.[{{Cite web|url=https://www.flashmemorysummit.com/English/Collaterals/Proceedings/2014/20140806_202E_Alves.pdf|title=In-Situ Processing Presentation|last=Alves|first=Vladimir|date=August 2014|access-date=24 May 2018|archive-date=28 November 2019|archive-url=https://web.archive.org/web/20191128024544/https://www.flashmemorysummit.com/English/Collaterals/Proceedings/2014/20140806_202E_Alves.pdf|url-status=live}}]
====Earth sciences====
In [Earth science](/source/Earth_science)s, particularly in [geomorphology](/source/geomorphology), ''in situ'' refers to natural materials or processes occurring at their point of origin without being transported. An example is [weathering](/source/weathering), in which rocks undergo physical or chemical disintegration in place,[{{cite book |last=Twidale |first=C.R. |author-link=Charles Rowland Twidale |year=1968 |chapter=Weathering |editor-last=Fairbridge |editor-first=R.W. |title=Geomorphology |series=Encyclopedia of Earth Science |publisher=[Springer Nature](/source/Springer_Nature) |location=Berlin, Heidelberg |doi=10.1007/3-540-31060-6_405 |quote=Weathering may be defined as the disintegration or decomposition of rocks ''in situ''. [...] But the main mass of the rock remains ''in situ'' and is not transported. |page=1228 |isbn=0-442-00939-9 }}] in contrast to [erosion](/source/erosion), which involves the removal and relocation of materials by agents such as wind, water, or ice.[{{cite book |last=Thornbury |first=William David |chapter=3. An Analysis of the Geomorphic Processes |title=Principles of Geomorphology |year=1954 |publisher=[Wiley](/source/Wiley_(publisher)) |pages=36–37 |url=https://books.google.com/books?id=_ywtAAAAIAAJ |via=[Google Books](/source/Google_Books) |oclc=1036826231 }}] [Soil](/source/Soil) formed from the weathering of underlying [bedrock](/source/bedrock) is an example of an ''in situ'' formation.[{{cite book |last1=Troeh |first1=F.R. |last2=Donahue |first2=R.L. |title=Dictionary of Agricultural and Environmental Science |year=2003 |publisher=[Iowa State Press](/source/Iowa_State_Press) |isbn=978-0-8138-0283-1 |url=https://books.google.com/books?id=doNtQgAACAAJ |via=[Google Books](/source/Google_Books) }}]{{rp|page=246}} ''In situ'' measurements, such as those of [soil moisture](/source/soil_moisture), rock stress, [groundwater](/source/groundwater) trends, or [radiation](/source/radiation) levels, are conducted on-site to provide direct data. These measurements are often essential for validating [remote sensing](/source/remote_sensing) data, such as [satellite imagery](/source/satellite_imagery), which is widely used for large-scale [environmental monitoring](/source/environmental_monitoring) but may require ''in situ'' confirmation to ensure accuracy.[{{cite journal |last1=Pause |first1=Marion |last2=Schweitzer |first2=Christian |last3=Rosenthal |first3=Michael |last4=Keuck |first4=Vanessa |last5=Bumberger |first5=Jan |last6=Dietrich |first6=Peter |last7=Heurich |first7=Marco |last8=Jung |first8=András |last9=Lausch |first9=Angela |title=In Situ/Remote Sensing Integration to Assess Forest Health—A Review |journal=[Remote Sensing](/source/Remote_Sensing_(journal)) |volume=8 |issue=6 |page=471 |year=2016 |doi=10.3390/rs8060471 |doi-access=free |bibcode=2016RemS....8..471P }}][{{cite journal |last1=Babaeian |first1=E. |last2=Sadeghi |first2=M. |last3=Jones |first3=S. B. |last4=Montzka |first4=C. |last5=Vereecken |first5=H. |last6=Tuller |first6=M. |year=2019 |title=Ground, proximal, and satellite remote sensing of soil moisture |journal=[Reviews of Geophysics](/source/Reviews_of_Geophysics) |volume=57 |issue=2 |pages=530–616 |doi=10.1029/2018RG000618 |doi-access=free |bibcode=2019RvGeo..57..530B }}][{{cite journal |last1=Xiao |first1=R. |last2=He |first2=X. |last3=Zhang |first3=Y. |last4=Ferreira |first4=V. G. |last5=Chang |first5=L. |year=2015 |title=Monitoring Groundwater Variations from Satellite Gravimetry and Hydrological Models: A Comparison with in-situ Measurements in the Mid-Atlantic Region of the United States |journal=[Remote Sensing](/source/Remote_Sensing_(journal)) |volume=7 |issue=1 |pages=686–703 |doi=10.3390/rs70100686 |doi-access=free |bibcode=2015RemS....7..686X }}]
[[File:CTD-me-details hg.jpg|thumb|Disassembled [CTD device](/source/CTD_(instrument)), showing pressure housing, sensor cage, connectors, and internal electronics with sensors for [conductivity](/source/Electrical_resistivity_and_conductivity), temperature, and pressure]]
In [oceanography](/source/oceanography), ''in situ'' observational methods involve direct measurements of oceanic conditions, typically conducted during shipboard surveys. These methods employ specialized instruments, such as the [Conductivity, Temperature, and Depth (CTD) device](/source/CTD_(instrument)), which records parameters such as [salinity](/source/salinity), temperature, [pressure](/source/pressure), and [biogeochemical](/source/biogeochemical) properties like [oxygen saturation](/source/oxygen_saturation).[{{cite web |url=https://oceanexplorer.noaa.gov/technology/ctd/ctd.html |title=Conductivity, Temperature, and Depth (CTD) |website=NOAA Ocean Explorer |publisher=[National Oceanic and Atmospheric Administration](/source/National_Oceanic_and_Atmospheric_Administration) (NOAA) |access-date=21 February 2025 |archive-date=7 February 2025 |archive-url=https://web.archive.org/web/20250207080104/https://oceanexplorer.noaa.gov/technology/ctd/ctd.html |url-status=live }}] Historically, oceanographers used [reversing thermometer](/source/reversing_thermometer)s, which were inverted at specific depths to trap [mercury](/source/Mercury_(element)) and preserve temperature readings for subsequent analysis.[{{cite book |last1=Affholder |first1=M. |last2=Valiron |first2=F. |title=Descriptive Physical Oceanography |chapter=Oceanographic Instruments and Methods |publisher=[CRC Press](/source/CRC_Press) |year=2001 |pages=61–63 |isbn=978-0-203-96927-4 |url=https://books.google.com/books?id=2NC3JmKI7mYC |access-date=21 February 2025 |via=[Google Books](/source/Google_Books) }}] These instruments have been largely replaced by {{Abbr|CTD|Conductivity, Temperature, and Depth}} devices and [expendable bathythermograph](/source/expendable_bathythermograph)s.[{{Cite web |title=History: Timeline |website=NOAA Ocean Explorer |publisher=[National Oceanic and Atmospheric Administration](/source/National_Oceanic_and_Atmospheric_Administration) (NOAA) |url=https://oceanexplorer.noaa.gov/history/timeline/?page=3 |access-date=21 February 2025}}]
{{Anchor|atmospheric science}}
In [atmospheric science](/source/atmospheric_science)s, ''in situ'' measurements refer to observations of atmospheric properties obtained using instruments placed within the environment being studied. Aircraft, balloons, and rockets are used to carry some of these instruments, allowing for direct interaction with the air to collect data.[{{cite book |last=Robinson |first=Rod |editor1-last=Jackson |editor1-first=Andrea V. |editor2-last=Hewitt |editor2-first=C. Nick |chapter=Atmospheric Monitoring Techniques |title=Handbook of Atmospheric Science: Principles and Applications |edition=1st illustrated |date=2003 |page=464 |publisher=Wiley |isbn=978-0-632-05286-8 |url=https://books.google.com/books?id=f51QCiiAWYQC |access-date=21 February 2025 |via=[Google Books](/source/Google_Books) }}] For example, [radiosonde](/source/radiosonde)s, carried aloft by [weather balloon](/source/weather_balloon)s, measure atmospheric parameters such as temperature, humidity, and pressure as they ascend through the [atmosphere](/source/atmosphere),[{{cite book |last1=Strahler |first1=Alan H. |title=Introducing Physical Geography |edition=6th |publisher=Wiley |year=2013 |isbn=978-111-839620-9 |page=156 |chapter=Chapter 5. Winds and Global Circulation }}] In contrast, remote sensing techniques, such as [weather radar](/source/weather_radar) and satellite observations, collect atmospheric data from a distance by using [electromagnetic radiation](/source/electromagnetic_radiation) to infer properties without direct contact with the atmosphere.[{{cite journal |last1=Bluestein |first1=H. B. |last2=Carr |first2=F. H. |last3=Goodman |first3=S. J. |year=2022 |title=Atmospheric Observations of Weather and Climate |journal=Atmosphere-Ocean |publisher=[Taylor & Francis](/source/Taylor_%26_Francis) |volume=60 |issue=3–4 |pages=149–187 |doi=10.1080/07055900.2022.2082369 |bibcode=2022AtO....60..149B }}]
====Materials science====
{{Further|In situ electron microscopy}}
By the mid-1980s, the term ''in situ'' was adopted in [materials science](/source/materials_science), particularly in the field of [heterogeneous catalysis](/source/heterogeneous_catalysis), where a [catalyst](/source/catalyst) in one [phase](/source/Phase_(matter)) facilitates a [chemical reaction](/source/chemical_reaction) in a different phase. The term later expanded beyond catalysis and is now applied across various disciplines of materials science, alongside the opposite designation ''ex situ''.[{{rp|page=1534}} For example, ''in situ'' describes the study of a [sample](/source/Sample_(material)) maintained in a [steady state](/source/steady_state){{efn|In sample characterization terminology, a system is in a ''steady state'' condition when one or more of its characteristics remain constant over time. This condition does not necessarily correspond to [thermodynamic equilibrium](/source/thermodynamic_equilibrium).][{{rp|page=1533}}}}
condition within a controlled environment, where specific parameters such as temperature or [pressure](/source/pressure) are regulated. This approach allows researchers to observe materials under conditions that replicate their functional states. Examples include a sample held at a fixed temperature inside a [cryostat](/source/cryostat), an [electrode](/source/electrode) material operating within an [electric battery](/source/electric_battery), or a specimen enclosed within a sealed container to protect it from external influences.][{{rp|page=1532}}
In [transmission electron microscopy](/source/transmission_electron_microscopy) (TEM) and [scanning transmission electron microscopy](/source/scanning_transmission_electron_microscopy) (STEM), ''in situ'' refers to the observation of materials as they are exposed to external stimuli within the microscope, under conditions that mimic their natural environments. This enables real-time observation of material behavior at the [nanoscale](/source/nanoscale). External stimuli in ''in situ'' {{Abbr|TEM|Transmission electron microscopy}}/{{Abbr|STEM|Scanning transmission electron microscopy}} experiments may include mechanical loading, pressure, temperature variation, electrical [biasing](/source/biasing), radiation, and environmental exposure to gases, liquids, or [magnetic field](/source/magnetic_field)s, individually or in combination. These conditions allow researchers to study atomic-level processes, such as [phase transformation](/source/phase_transformation)s, chemical reactions, and [mechanical deformations](/source/Plasticity_(physics)).][{{cite book |doi=10.1002/9783527834822.ch1 |page=3 |title=In-Situ Transmission Electron Microscopy Experiments |chapter=Chapter 1. In-Situ TEM |date=2023 |last1=Sharma |first1=Renu |isbn=978-3-527-34798-8 }}][{{cite journal |last1=Sharma |first1=Renu |last2=Yang |first2=Wei-Chang David |title=Perspective and prospects of in situ transmission/scanning transmission electron microscopy |journal=Microscopy |date=8 April 2024 |volume=73 |issue=2 |page=79 |doi=10.1093/jmicro/dfad057 |pmid=38006307 }}]
====Medicine====
{{anchor|cancer}}
{{Further|Carcinoma in situ}}
{{Seealso|In situ lymphoid neoplasia|List of medical roots, suffixes and prefixes}}
In [medical terminology](/source/medical_terminology), ''in{{nbsp}}situ'' belongs to a group of two-word [Latin](/source/Latin) expressions, including ''[in vitro](/source/in%26nbsp%3Bvitro)'' ('within the glass', e.g., laboratory experiments), ''[in vivo](/source/in%26nbsp%3Bvivo)'' ('within the living', e.g., experiments on living [organism](/source/organism)s), and ''[ex vivo](/source/ex%26nbsp%3Bvivo)'' ('out of the living', e.g., experiments on [extracted tissue](/source/Biopsy)s). These expressions facilitate concise communication of experimental and clinical contexts, much like abbreviations. ''In{{nbsp}}situ'' is widely used in medicine to describe phenomena or processes occurring in their original location. Its applications span [oncology](/source/oncology), measurement acquisition, [medical simulation](/source/medical_simulation), and anatomical examination. Because of its versatility across such varied uses, one study has described ''in{{nbsp}}situ'' as among the most productive Latin expressions in contemporary medical discourse.[{{cite journal | doi=10.1186/s13256-018-1562-x | doi-access=free | title=The use of Latin terminology in medical case reports: Quantitative, structural, and thematic analysis | date=2018 | last1=Lysanets | first1=Yuliia V. | last2=Bieliaieva | first2=Olena M. | journal=[Journal of Medical Case Reports](/source/Journal_of_Medical_Case_Reports) | volume=12 | issue=1 | page=45 | pmid=29471882 | pmc=5824564 }}]
[[File:In situ carcinoma-en.svg|thumb|Diagram of an [''in situ'' carcinoma](/source/Carcinoma_in_situ), not having invaded beyond the [basement membrane](/source/basement_membrane)]]
In oncology, ''in situ'' is applied in the context of [carcinoma ''in situ''](/source/Carcinoma_in_situ) (CIS), a term describing abnormal cells confined to their original location without [invasion](/source/Invasion_(cancer)) of surrounding tissue.[{{cite encyclopedia |title=carcinoma in situ |url=https://www.cancer.gov/publications/dictionaries/cancer-terms/def/carcinoma-in-situ |encyclopedia=NCI Dictionary of Cancer Terms |publisher=[National Cancer Institute](/source/National_Cancer_Institute) |access-date=2024-11-05 |archive-date=15 October 2024 |archive-url=https://web.archive.org/web/20241015055152/https://www.cancer.gov/publications/dictionaries/cancer-terms/def/carcinoma-in-situ |url-status=live }}] The earliest known use of the term dates back to 1932 in the writing of U.S. surgical pathologist [Albert C. Broders](/source/Albert_C._Broders), who introduced both the term and the concept.[{{cite journal |last=Wright |first=James R. Jr. |title=Albert C. Broders' paradigm shifts involving the prognostication and definition of cancer |journal=[Archives of Pathology & Laboratory Medicine](/source/Archives_of_Pathology_%26_Laboratory_Medicine) |date=2012 |volume=136 |issue=11 |pages=1437–1446 |doi=10.5858/arpa.2011-0567-HP |pmid=23106590 }}] {{Abbr|CIS|Carcinoma in situ}} is a critical term in early [cancer diagnosis](/source/cancer_diagnosis), as it signifies a non-invasive stage, allowing for more targeted interventions such as localized excision or monitoring—before potential progression to invasive cancer.[{{cite journal |last=Allred |first=D. C. |date=2010 |title=Ductal carcinoma in situ: terminology, classification, and natural history |journal=[Journal of the National Cancer Institute Monographs](/source/Journal_of_the_National_Cancer_Institute_Monographs) |issue=41 |pages=134–138 |doi=10.1093/jncimonographs/lgq035|pmid=20956817 |pmc=5161057 }}][{{cite journal | doi=10.1038/s41392-024-01779-3 | title=Progression from ductal carcinoma in situ to invasive breast cancer: Molecular features and clinical significance | date=2024 | last1=Wang | first1=Jing | last2=Li | first2=Baizhou | last3=Luo | first3=Meng | last4=Huang | first4=Jia | last5=Zhang | first5=Kun | last6=Zheng | first6=Shu | last7=Zhang | first7=Suzhan | last8=Zhou | first8=Jiaojiao | journal=[Signal Transduction and Targeted Therapy](/source/Signal_Transduction_and_Targeted_Therapy) | volume=9 | issue=1 | page=83 | pmid=38570490 | pmc=10991592 }}] Melanoma ''in{{nbsp}}situ'' is an early, localized form of [melanoma](/source/melanoma) (a type of malignant [skin cancer](/source/skin_cancer)). In this stage, the cancerous [melanocyte](/source/melanocyte)s (the pigment-producing cells that give skin its color) are confined to the [epidermis](/source/epidermis), the outermost layer of the skin; the melanoma has not yet penetrated into the deeper [dermal layer](/source/dermal_layer)s or metastasized to other parts of the body.[{{cite book|title=Histological Diagnosis of Nevi and Melanoma |url=https://books.google.com/books?id=G_zEBAAAQBAJ |first1=Guido |last1=Massi |first2=Philip E. |last2=LeBoit |year=2013 |via=[Google Books](/source/Google_Books) |isbn=978-3-642-37311-4 |publisher=[Springer](/source/Springer_Publishing) |page=421 |chapter=Chapter 28. Melanoma in Situ }}]
Beyond oncology, ''in situ'' is used in fields where maintaining natural anatomical or physiological positions is essential.[{{cite journal | doi=10.1186/1752-1947-6-136 | doi-access=free | title=A novel diagnostic sign of hip fracture mechanism in ground level falls: Two case reports and review of the literature | date=2012 | last1=Kelly | first1=Douglas W. | last2=Kelly | first2=Brian D. | journal=[Journal of Medical Case Reports](/source/Journal_of_Medical_Case_Reports) | volume=6 | article-number=136 | pmid=22643013 | pmc=3423009 }}] In [cardiothoracic surgery](/source/cardiothoracic_surgery), ''in situ'' often describes techniques where [blood vessel](/source/blood_vessel)s are utilized in their original anatomical position for surgical purposes. For example, the [internal thoracic artery](/source/internal_thoracic_artery) can be left attached to the [subclavian artery](/source/subclavian_artery) while rerouting blood flow to bypass occluded [coronary arteries](/source/coronary_arteries) and improve heart circulation.[{{cite journal |last1=Fukui |first1=Toshihiro |last2=Takanashi |first2=Shuichiro |last3=Hosoda |first3=Yasuyuki |last4=Suehiro |first4=Shigefumi |title=In situ bilateral skeletonized internal thoracic arterial grafting for left-side myocardial revascularization using an off-pump technique |journal=Interactive CardioVascular and Thoracic Surgery |volume=5 |issue=4 |pages=413–417 |date=August 2006 |doi=10.1510/icvts.2006.128512 |pmid=17670604 }}][{{cite journal |last1=Kawajiri |first1=Hidetake |last2=Grau |first2=Juan B |last3=Fortier |first3=Jacqueline H |last4=Glineur |first4=David |title=Bilateral internal thoracic artery grafting: in situ or composite? |journal=Annals of Cardiothoracic Surgery |volume=7 |issue=5 |pages=673–680 |date=September 2018 |doi=10.21037/acs.2018.05.16 |doi-access=free |pmc=6219951 |pmid=30505752 }}] In [organ transplantation](/source/organ_transplantation), ''in situ'' is used to describe procedures performed within the donor's body to preserve organ viability. ''In situ'' [perfusion](/source/perfusion) is a technique employed during organ retrieval to restore blood flow to organs while they remain in their original location. This method minimizes [ischemic injury](/source/ischemic_injury) and preserves organ viability for transplantation. In contrast, ''ex situ'' [machine perfusion](/source/machine_perfusion) involves perfusing the organ outside the donor's body, typically after it has been removed.[{{cite journal |last1=Jochmans |first1=I. |last2=Akhtar |first2=M. Z. |last3=Nasralla |first3=D. |last4=Kocabayoglu |first4=P. |last5=Boffa |first5=C. |last6=Kaisar |first6=M. |last7=Brat |first7=A. |last8=O'Callaghan |first8=J. |last9=Pengel |first9=L. H. M. |last10=Knight |first10=S. |last11=Ploeg |first11=R. J. |title=Past, Present, and Future of Dynamic Kidney and Liver Preservation and Resuscitation |journal=[American Journal of Transplantation](/source/American_Journal_of_Transplantation) |volume=16 |issue=9 |pages=2545–2555 |date=September 2016 |doi=10.1111/ajt.13778 |pmid=26946212}}][{{cite journal |last1=Reznik |first1=O. |last2=Skvortsov |first2=A. |last3=Loginov |first3=I. |last4=Ananyev |first4=A. |last5=Bagnenko |first5=S. |last6=Moysyuk |first6=Y. |title=Kidney from uncontrolled donors after cardiac death with one hour warm ischemic time: resuscitation by extracorporal normothermic abdominal perfusion "in situ" by leukocytes-free oxygenated blood |journal=Clinical Transplantation |volume=25 |issue=4 |pages=511–516 |date=July–August 2011 |doi=10.1111/j.1399-0012.2010.01333.x |pmid=20626704}}]{{efn|See ''[ex vivo](/source/ex_vivo)''.}}
====Petroleum engineering====
{{Further|Steam-assisted gravity drainage}}
In [petroleum engineering](/source/petroleum_engineering), ''in situ'' techniques involve the application of heat or [solvent](/source/solvent)s to extract [heavy crude oil](/source/heavy_crude_oil) or [bitumen](/source/bitumen) from reservoirs located beneath the [Earth's surface](/source/Earth's_surface). Several ''in situ'' methods exist, but those that utilize heat, particularly steam, have proven to be the most effective for [oil sands](/source/oil_sands) extraction. The most widely used ''in situ'' technique is [steam-assisted gravity drainage](/source/steam-assisted_gravity_drainage) (SAGD).[{{cite web |title=Oil Sands Extraction and Processing |url=https://natural-resources.canada.ca/energy-sources/fossil-fuels/oil-sands-extraction-processing |url-status=live |archive-url=https://web.archive.org/web/20250303185847/https://natural-resources.canada.ca/energy-sources/fossil-fuels/oil-sands-extraction-processing |website=[Natural Resources Canada](/source/Natural_Resources_Canada) |date=16 January 2025 |archive-date=3 March 2025 |access-date=3 March 2025 }}] This method employs two horizontal wells: the upper well injects steam to heat the bitumen, reducing its viscosity, while the lower well collects the mobilized oil for extraction.[{{cite web |last1=Ahtian |first1=Sourabh |last2=Irani |first2=Mazda |last3=de Haas |first3=Tom |last4=Abedini |first4=Ali |title=In Situ Methods for Bitumen Extraction: An Overview |url=https://www.interfacefluidics.com/in-situ-methods-for-bitumen-extraction-an-overview/ |website=Interface Fluidics |date=23 September 2020 |access-date=3 March 2025 |archive-date=3 November 2024 |archive-url=https://web.archive.org/web/20241103041805/https://www.interfacefluidics.com/in-situ-methods-for-bitumen-extraction-an-overview/ |url-status=live }}] {{Abbr|SAGD|Steam-assisted gravity drainage}} has gained prominence in the Canadian province of [Alberta](/source/Alberta), due to its efficiency in recovering bitumen from deep reservoirs. Approximately 80% of Alberta's oil sands deposits are located at depths that render [open-pit mining](/source/open-pit_mining) impractical, making ''in situ'' techniques such as {{Abbr|SAGD|Steam-assisted gravity drainage}} the primary method of extraction.[{{cite web | title = Steam Assisted Gravity Drainage: Facts and Stats | url = https://open.alberta.ca/dataset/f7c779ea-9776-4d59-a1b3-178d533f0ebc/resource/aac73d46-3ae0-478e-9b19-e64afa41b1f2/download/fssagd.pdf |website = open.alberta.ca | publisher = [Government of Alberta](/source/Government_of_Alberta) |date=November 2013 |access-date = 24 February 2025 |archive-url=https://web.archive.org/web/20240304205256/https://open.alberta.ca/dataset/f7c779ea-9776-4d59-a1b3-178d533f0ebc/resource/aac73d46-3ae0-478e-9b19-e64afa41b1f2/download/fssagd.pdf |archive-date=4 March 2024 }}]
====Urban planning====
In [urban planning](/source/urban_planning), ''in situ'' upgrading is an approach to and method of upgrading [informal settlement](/source/informal_settlement)s.[{{cite journal|last1=Huchzermeyer|first1=Marie|title=The struggle for in situ upgrading of informal settlements: A reflection on cases in Gauteng|journal=[Development Southern Africa](/source/Development_Southern_Africa) |date=2009|volume=26|issue=1|pages=59–74|doi=10.1080/03768350802640099|s2cid=153687182}}]
===Humanities===
==== Archaeology====
[[File:Hohokam Arrowhead Sahuarita Arizona 2014.jpg|thumb|A [Hohokam](/source/Hohokam) arrowhead ''in situ'']]
In [archaeology](/source/archaeology), the term ''in situ'' has been used variably to describe [artifacts](/source/Artifact_(archaeology)) or [features](/source/Feature_(archaeology)) found undisturbed since deposition; however, its definition remains contested. Scholars distinguish between a broad usage, referring to materials recovered through controlled [excavation](/source/Archaeological_excavation), and a stricter usage applied only to those discovered in undisturbed depositional settings.[{{cite journal |last1=Archer |first1=Will |last2=Aldeias |first2=Vera |last3=McPherron |first3=Shannon P. |title=What is 'in situ'? A reply to Harmand et al. (2015) |journal=[Journal of Human Evolution](/source/Journal_of_Human_Evolution) |date=2020 |volume=142 |article-number=102740 |doi=10.1016/j.jhevol.2020.102740 |pmid=32247106 |bibcode=2020JHumE.14202740A }}] Recording the exact [spatial coordinates](/source/Spatial_reference_system), stratigraphic position, and surrounding matrix of depositional materials is necessary for understanding past human activities and historical processes. While artifacts are often removed for analysis, certain archaeological features—such as [hearth](/source/hearth)s, [posthole](/source/posthole)s, and [architectural foundations](/source/architectural_foundations)—have to be thoroughly documented in place to preserve their contextual information during excavation.[{{cite book |title=Archaeology: Theories, Methods and Practice |first1=Colin |last1=Renfrew |author-link1=Colin Renfrew |first2=Paul |last2=Bahn |date=2020 |author-link2=Paul Bahn |isbn=978-0-500-29424-6 |edition=8th |publisher=[Thames & Hudson](/source/Thames_%26_Hudson) |location=London }}]{{rp|page=121}} This documentation relies on various methods, including detailed field notes, scaled [technical drawing](/source/technical_drawing)s, [cartographic](/source/cartographic) representation, and high-resolution photographic records. Current archaeological practice incorporates advanced digital technologies, including [3D laser scanning](/source/3D_laser_scanning), [photogrammetry](/source/photogrammetry), [unmanned aerial vehicles](/source/unmanned_aerial_vehicles), and [Geographic Information Systems](/source/Geographic_Information_Systems) (GIS), to capture complex spatial relationships.[{{Cite journal|title=An Innovative System for Enhancing Archaeological In Situ Excavation through Geospatial Integration|first1=Asimina|last1=Dimara|first2=Sotirios|last2=Tsakiridis|first3=Doukas|last3=Psarros|first4=Alexios|last4=Papaioannou|first5=Dimitrios|last5=Varsamis|first6=Christos-Nikolaos|last6=Anagnostopoulos|first7=Stelios|last7=Krinidis|date=24 May 2024 |journal=Heritage|volume=7|issue=5|pages=2586–2619|doi=10.3390/heritage7050124 |doi-access=free }}] Artifacts found outside their original context (''ex situ''), often due to natural disturbances or amateur excavations, have less interpretive value, but may provide clues about the spatial distribution and typological characteristics of unexcavated ''in situ'' deposits, guiding future excavation efforts.[{{Cite web|url=https://archdenk.rkarl.org/2019/01/an-empirical-examination-of.html?m=1 |archive-url=https://web.archive.org/web/20240511051111/https://archdenk.rkarl.org/2019/01/an-empirical-examination-of.html?m=1 |archive-date=11 May 2024 |title=An empirical examination of archaeological damage caused by unprofessional extraction of archaeology ex situ ('looting'): A case study from Austria |first=Raimund |last=Karl |author-link=Raimund Karl |date=2 January 2019 |publisher=Archäologische Denkmalpflege |pages=1–2 |access-date=2024-10-24 }}][{{Cite journal|title=Coastal curios? An analysis of ex situ beach finds for mapping new Palaeolithic sites at Happisburgh, UK|first1=Rachel|last1=Bynoe|first2=Nick M.|last2=Ashton|first3=Tim|last3=Grimmer|first4=Peter|last4=Hoare|first5=Joanne|last5=Leonard|first6=Simon G.|last6=Lewis|first7=Darren|last7=Nicholas|first8=Simon|last8=Parfitt|date=February 24, 2021|journal=[Journal of Quaternary Science](/source/Journal_of_Quaternary_Science) |volume=36|issue=2|pages=191–210|doi=10.1002/jqs.3270|bibcode=2021JQS....36..191B |doi-access=free}}]
The [Convention on the Protection of the Underwater Cultural Heritage](/source/Convention_on_the_Protection_of_the_Underwater_Cultural_Heritage) sets mandatory guidelines for signatory states regarding the treatment of [underwater shipwrecks](/source/Underwater_archaeology). One of its main principles is that ''in situ'' preservation is the preferred approach.[{{cite web |title=The UNESCO Convention on the Protection of the Underwater Cultural Heritage |url=https://unesdoc.unesco.org/ark:/48223/pf0000152883 |year=2007 |access-date=2024-10-12 |website=UNESCO Digital Library |publisher=[UNESCO](/source/UNESCO) |archive-date=28 August 2024 |archive-url=https://web.archive.org/web/20240828104155/https://unesdoc.unesco.org/ark:/48223/pf0000152883 |url-status=live }}]{{rp|page=13}} This policy is based on the unique conditions of underwater environments, where low [oxygen level](/source/oxygen_level)s and stable temperatures help preserve artifacts over long periods. Removing artifacts from these conditions and exposing them to the atmosphere often accelerates deterioration, particularly the [oxidation](/source/oxidation) of iron-based materials.[{{cite journal |last1=Tuller |first1=Hugh |last2=Đurić' |first2=Marija |title=Keeping the pieces together: Comparison of mass grave excavation methodology |journal=[Forensic Science International](/source/Forensic_Science_International) |date=January 2006 |volume=156 |issue=2–3 |page=193 |doi=10.1016/j.forsciint.2004.12.033 |pmid=15896937 }}]
====Art====
{{Further|Site-specific art|Land art}}
{{Broader|Installation art}}
[[File:"The Mastaba" massive sculpture, floating in the Serpentine (geograph 5815024).jpg|thumb|right|Many of [Christo and Jeanne-Claude](/source/Christo_and_Jeanne-Claude)'s temporary [installations](/source/Installation_art), such as ''The London Mastaba'' (pictured), exemplify ''in situ'' approach in art.]]
The concept of ''in situ'' in [contemporary art](/source/contemporary_art) developed in the late 1960s and 1970s, referring to works created for a specific site. Such works incorporate the site's physical, historical, political, and sociological characteristics as integral elements of their composition.[{{cite encyclopedia|encyclopedia=Dictionary of Untranslatables: A Philosophical Lexicon |editor-first=Barbara |editor-last=Cassin |editor-link=Barbara Cassin |title=IN SITU (LATIN) |last=Riout |first=Denys |date=9 February 2014 |publisher=[Princeton University Press](/source/Princeton_University_Press) |page=484 |isbn=978-1-4008-4991-8 }}] Theoretical discussions, particularly in the writings and practice of French [conceptual artist](/source/conceptual_artist) and sculptor [Daniel Buren](/source/Daniel_Buren), have addressed the dynamic relationship between artistic intervention and its surrounding environment.[{{cite book|title=Arts, Ecologies, Transitions: Constructing a Common Vocabulary |first=Lorraine |last=Verner |editor-last1=Barbanti |editor-first1=Roberto |editor-last2=Ginot |editor-first2=Isabelle |editor-last3=Solomos |editor-first3=Makis |editor-last4=Sorin |editor-first4=Cécile |chapter=40. Site Specificity |isbn=978-1-003-85240-7 |publisher=[Taylor & Francis](/source/Taylor_%26_Francis) |year=2024 |url=https://books.google.com/books?id=J2fwEAAAQBAJ |via=[Google Books](/source/Google_Books) |access-date=2024-10-24 }}]{{rp|page=161}}[{{cite web
| title = In Situ—The Eye of the Storm: Works In Situ by Daniel Buren
| website = guggenheim.org
| publisher = [Solomon R. Guggenheim Foundation](/source/Solomon_R._Guggenheim_Foundation)
| url = https://www.guggenheim.org/teaching-materials/the-eye-of-the-storm-works-in-situ-by-daniel-buren/in-situ
| access-date = 16 October 2025
}}]
The site-specific [installations](/source/Installation_art) of [Christo and Jeanne-Claude](/source/Christo_and_Jeanne-Claude) exemplify the application of ''in situ'' principles in art. Their large-scale interventions such as ''[The Pont Neuf Wrapped](/source/The_Pont_Neuf_Wrapped)'' (1985) and ''[Wrapped Reichstag](/source/Wrapped_Reichstag)'' (1995) involved the systematic wrapping of buildings and landscape elements in fabric, temporarily transforming familiar spaces and altering public perception. Another example is the [land art](/source/land_art) movement, wherein artists such as [Robert Smithson](/source/Robert_Smithson) and [Michael Heizer](/source/Michael_Heizer) integrated their works directly into natural landscapes.[{{cite journal|last= Fong | first = Peter K. W. | title = Issues in Urban Redevelopment: The Land Development Corporation | journal = Built Environment | volume = 11 | issue = 4 | year = 1985 |pages= 283–293 |publisher=Alexandrine Press |jstor = 23286194 }}]{{rp|pages=283–285}}[{{Cite web|url=https://www.devb.gov.hk/en/publications_and_press_releases/press/index_id_12712.html |archive-url=https://web.archive.org/web/20250122025215/https://www.devb.gov.hk/en/publications_and_press_releases/press/index_id_12712.html |archive-date=22 January 2025 |url-status=live |title=DEVB Press Releases: Revised in-situ land exchange arrangements for Northern Metropolis to enhance speed and efficiency by leveraging market forces |website=devb.gov.hk |year=2021 |access-date=6 November 2024 |publisher=[Development Bureau](/source/Development_Bureau) }}][{{cite web |title=In-situ land exchange to enable harbourfront development at Quarry Bay by private lot owner |url=https://www.info.gov.hk/gia/general/202103/03/P2021030300443.htm |publisher=The Government of the Hong Kong Special Administrative Region |date=3 March 2021 |access-date=3 March 2025 |archive-date=30 December 2022 |archive-url=https://web.archive.org/web/20221230205956/https://www.info.gov.hk/gia/general/202103/03/P2021030300443.htm |url-status=live }}]
In [public international law](/source/public_international_law), the term ''in situ'' is used to distinguish between a government that exercises effective control over a state's territory and population and a [government-in-exile](/source/government-in-exile), which operates from outside its national borders. A government ''in situ'' is the ''[de facto](/source/de_facto)'' governing authority, while a government-in-exile may still claim legitimacy despite lacking territorial control. The recognition of a government generally depends on its ability to maintain authority over its state, though exceptions exist, particularly when a government-in-exile is displaced due to unlawful [foreign occupation](/source/foreign_occupation).[{{cite book |last=Pavlopoulos |first=Niko |chapter=The International Legal Criteria for Governmental Status |title=The Identity of Governments in International Law |date=2024 |pages=94–141 |chapter-url=https://www.ilsa.org/Jessup/Jessup2025/Basic%20Materials/Chapter%204.pdf |url-status=live |archive-url=https://web.archive.org/web/20241005031527/https://www.ilsa.org/Jessup/Jessup2025/Basic%20Materials/Chapter%204.pdf |archive-date=5 October 2024 |publisher=[Oxford University Press](/source/Oxford_University_Press) |doi= 10.1093/9780191991509.003.0004 |isbn=978-0-19-199150-9 |via=www.ilsa.org |access-date=3 March 2025}}]{{rp|pages=115–117}}[{{cite book |last=Talmon |first=Stefan |author-link=Stefan Talmon |title=Recognition of Governments in International Law: With Particular Reference to Governments in Exile |series=Oxford Monographs in International Law |year=2001 |chapter=Preliminary Considerations |publisher=[Oxford University Press](/source/Oxford_University_Press) |isbn=978-0-19-924839-1}}]{{rp|page=2}}
====Linguistics====
{{Broader|English interrogative words}}
In [linguistics](/source/linguistics), particularly in [syntax](/source/syntax), an element is described as ''in situ'' when it is pronounced in the same position where it receives its [semantic interpretation](/source/semantic_interpretation). This concept is especially relevant in the analysis of ''wh-'' questions across languages. For example, in [Mandarin Chinese](/source/Mandarin_Chinese) and [Kurdish](/source/Kurdish_language), wh-elements remain ''in situ'', producing structures analogous to "John bought what?" where the [interrogative word](/source/interrogative_word) occupies the same syntactic position as the direct [object](/source/Object_(grammar)) would in a [declarative sentence](/source/declarative_sentence) ("John bought bread").[{{Cite journal |last = Liu |first = Chi-Ming Louis | date = January 2023 | title = (Embedded) short answers to wh-questions in Mandarin Chinese | journal = Journal of East Asian Linguistics | volume = 31 | issue = 3 | pages = 351–399 | doi = 10.1007/s10831-022-09242-6 }}][{{Cite journal | last = Toma | first = Shivan | date = March 2020 | title = From Wh-Movement to Wh-In-Situ Acquisition of I-To-C Movement in English Interrogative Constructions by Kurdish Learners | journal = Humanities Journal of University of Zakho | volume = 8 | issue = 1 | pages = 159–171 | doi = 10.26436/hjuoz.2020.8.1.585 | doi-access = free }}] By contrast, languages like English and French typically employ [wh-movement](/source/wh-movement), where the interrogative element is displaced from its base position to the beginning of the clause, as in "What did John buy?" Here, the wh-word ''{{linktext|what}}'' has moved from its original post-verbal position to the sentence-initial position, leaving behind a trace or gap in the object position. This [typological](/source/typological) distinction between ''in situ'' wh-elements and moved wh-elements represents one of the fundamental parameters of variation in natural language syntax and has been extensively studied within [generative grammar](/source/generative_grammar) frameworks.
===Social sciences===
====Economics====
In [economics](/source/economics), ''in situ storage'' refers to the practice of retaining a product, usually a [natural resource](/source/natural_resource), in its original location rather than extracting and storing it elsewhere. This method avoids direct [out-of-pocket cost](/source/out-of-pocket_cost)s, such as those for transportation or storage facilities, with the primary expense being the [opportunity cost](/source/opportunity_cost) of delaying potential [revenue](/source/revenue). It applies to resources like oil and gas left unextracted in wells, [mineral](/source/mineral)s and [gemstone](/source/gemstone)s remaining underground, and timber left standing until extraction is economically favorable. Certain agricultural products, such as [hay](/source/hay), can be stored ''in situ'' under suitable conditions.[{{cite book |last=Dorfman |first=Jeffrey |chapter=5. The economics of storage |title=Economics and Management of the Food Industry |series=Routledge Textbooks in Environmental and Agricultural Economics |publisher=[Routledge](/source/Routledge) |year=2014 |isbn=978-1-134-45656-7 |url=https://books.google.com/books?id=b-4jAwAAQBAJ |via=[Google Books](/source/Google_Books) |access-date=3 March 2025 }}]{{rp|page=54}}[{{cite book |last1=Barbosa-Cánovas |first1=Gustavo V. |author-link1=Gustavo V. Barbosa-Cánovas |last2=Fernández-Molina |first2=Juan J. |last3=Alzamora |first3=Stella M. |last4=Tapia |first4=Maria S. |last5=López-Malo |first5=Aurelio |title=Handling and Preservation of Fruits and Vegetables by Combined Methods for Rural Areas |url=https://books.google.com/books?id=IKsaRY9sb_AC |publisher=[Food and Agriculture Organization of the United Nations](/source/Food_and_Agriculture_Organization_of_the_United_Nations) |year=2003 |isbn=978-92-5-104861-0 |via=[Google Books](/source/Google_Books) |access-date=3 March 2025 }}]{{rp|page=35}}
====Psychology====
In [psychology](/source/psychology), ''in situ'' typically refers to studies conducted in a natural or real-world setting, as opposed to a controlled laboratory environment. This approach allows researchers to observe and measure psychological processes as they occur, increasing [ecological validity](/source/ecological_validity)—though often at the expense of experimental control over variables.[{{cite book |last=Stevenson |first=Andrew |year=2010 |title=Cultural Issues in Psychology: A Student's Handbook |publisher=[Routledge](/source/Routledge) |isbn=978-1-135-23984-8 |url=https://books.google.com/books?id=1cCNAgAAQBAJ |access-date=4 March 2025 |via=[Google Books](/source/Google_Books) }}]{{rp|pages=84–85}}
===Miscellaneous===
====Gastronomy====
In [gastronomy](/source/gastronomy), ''in situ'' refers to the art of cooking with the different resources that are available at the site of the event. Here a person is not going to the restaurant, but the restaurant comes to the person's home.[{{cite book|last1=Gillespie|first1=Cailein|last2=Cousins|first2=John A.|title=European Gastronomy into the 21st Century|date=2001|publisher=Elsevier|location=Oxford, UK|isbn=978-0-7506-5267-4|page=72|url=https://books.google.com/books?id=2G5cihKVlOIC&q=in+situ+gastronomy&pg=PA72|access-date=16 June 2014}}]
====Mining====
{{Main|In situ leach}}
''In situ'' leaching or ''in situ'' recovery refers to the mining technique of injecting [lixiviant](/source/lixiviant) underground to dissolve ore and bringing the pregnant leach solution to surface for extraction. Commonly used in uranium mining but has also been used for copper mining.[{{cite web |url=http://www.world-nuclear.org/info/inf27.html |title=In Situ Leach (ISL) Mining of Uranium |website=[World Nuclear Association](/source/World_Nuclear_Association) |publisher=world-nuclear.org |date=March 2008 |archive-url=https://web.archive.org/web/20090424213134/http://www.world-nuclear.org/info/inf27.html |archive-date=24 April 2009 |access-date=19 February 2025}}]
==See also==
{{Wiktionary}}
* [In situ conservation](/source/In_situ_conservation)
* [Ex situ conservation](/source/Ex_situ_conservation)
* [List of colossal sculptures in situ](/source/List_of_colossal_sculptures_in_situ)
* [List of Latin phrases](/source/List_of_Latin_phrases)
* {{annotated link|Neoclassical compound}}
* {{lookfrom}}
==Notes==
{{notelist}}
==References==
{{reflist}}
===Primary sources===
{{Reflist|group=†}}
Category:Animal test conditions
Category:Broad-concept articles
Category:Latin biological phrases
Category:Latin legal terminology
Category:Latin medical words and phrases
Category:Latin words and phrases
Category:Research
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Adapted from the Wikipedia article [In situ](https://en.wikipedia.org/wiki/In_situ) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/In_situ?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.