Editing In vitro (section)

===Simplicity===
Living organisms are extremely complex functional systems that are made up of, at a minimum, many tens of thousands of genes, protein molecules, RNA molecules, small organic compounds, inorganic ions, and complexes in an environment that is spatially organized by membranes, and in the case of multicellular organisms, organ systems.<ref>{{cite book |author=Alberts, Bruce |title=Molecular biology of the cell |publisher=Garland Science |location=New York |year=2008 |isbn=978-0-8153-4105-5 }}</ref><ref>{{Cite web |title=Biological Complexity and Integrative Levels of Organization {{!}} Learn Science at Scitable |url=http://www.nature.com/scitable/topicpage/biological-complexity-and-integrative-levels-of-organization-468 |access-date=2023-04-11 |website=www.nature.com |language=en}}</ref>  These myriad components interact with each other and with their environment in a way that processes food, removes waste, moves components to the correct location, and is responsive to signalling molecules, other organisms, light, sound, heat, taste, touch, and balance.
[[File:Vitrocell mammalian exposure module-smoking robot.jpg|thumbnail|right|Top view of a Vitrocell mammalian exposure module "smoking robot", (lid removed) view of four separated wells for cell culture inserts to be exposed to tobacco smoke or an [[aerosol]] for an ''in vitro'' study of the effects]]
This complexity makes it difficult to identify the interactions between individual components and to explore their basic biological functions. ''In vitro'' work simplifies the system under study, so the investigator can focus on a small number of components.<ref>{{cite book |author1=Vignais, Paulette M. |author2=Pierre Vignais |title=Discovering Life, Manufacturing Life: How the experimental method shaped life sciences |publisher=Springer |location=Berlin |year=2010 |isbn=978-90-481-3766-4 }}</ref><ref>{{cite book |author1=Jacqueline Nairn |author2=Price, Nicholas C. |title=Exploring proteins: a student's guide to experimental skills and methods |publisher=Oxford University Press |location=Oxford [Oxfordshire] |year=2009 |isbn=978-0-19-920570-7 }}</ref>

For example, the identity of proteins of the immune system (e.g. antibodies), and the mechanism by which they recognize and bind to foreign antigens would remain very obscure if not for the extensive use of ''in vitro'' work to isolate the proteins, identify the cells and genes that produce them, study the physical properties of their interaction with antigens, and identify how those interactions lead to cellular signals that activate other components of the immune system.