Editing Optical microscope (section)

==History==
{{See also|History of optics|Timeline of microscope technology}}

===Invention===
The earliest microscopes were single [[lens (optics)|lens]] [[magnifying glass]]es with limited magnification, which date at least as far back as the widespread use of lenses in [[eyeglasses]] in the 13th century.<ref>Atti Della Fondazione Giorgio Ronchi E Contributi Dell'Istituto Nazionale Di Ottica, Volume 30, La Fondazione-1975, page 554</ref>

Compound microscopes first appeared in Europe around 1620<ref>{{cite book|author1=Albert Van Helden|author2=Sven Dupré|author3=Rob van Gent|title=The Origins of the Telescope|url=https://books.google.com/books?id=XguxYlYd-9EC&pg=PA24|year=2010|publisher=Amsterdam University Press|isbn=978-90-6984-615-6|page=24}}</ref><ref name="J. William Rosenthal 1996, page 391"/> including one demonstrated by [[Cornelis Drebbel]] in London (around 1621) and one exhibited in Rome in 1624.<ref name="Raymond J. Seeger 2016, page 24">Raymond J. Seeger, Men of Physics: Galileo Galilei, His Life and His Works, Elsevier - 2016, page 24</ref><ref name="J. William Rosenthal 1996, page 391">J. William Rosenthal, Spectacles and Other Vision Aids: A History and Guide to Collecting, Norman Publishing, 1996, page 391–2</ref>

The actual inventor of the compound microscope is unknown although many claims have been made over the years. These include a claim 35<ref>{{cite book|author1=Albert Van Helden|author2=Sven Dupré|author3=Rob van Gent|title=The Origins of the Telescope|url=https://books.google.com/books?id=XguxYlYd-9EC&pg=PA36|year=2010|publisher=Amsterdam University Press|isbn=978-90-6984-615-6|pages=32–36, 43}}</ref> years after they appeared by [[Dutch people|Dutch]] spectacle-maker Johannes Zachariassen that his father, [[Zacharias Janssen]], invented the compound microscope and/or the telescope as early as 1590. Johannes' testimony, which some claim is dubious,<ref>[[#Van Helden|Van Helden]], p. 43</ref><ref name=Shmaefsky>Shmaefsky, Brian (2006) ''Biotechnology 101''. Greenwood. p. 171. {{ISBN|0313335281}}.</ref><ref>Note: stories vary, including Zacharias Janssen had the help of his father Hans Martens (or sometimes said to have been built entirely by his father). Zacharias' probable birth date of 1585 ([[#Van Helden|Van Helden]], p. 28) makes it unlikely he invented it in 1590 and the claim of invention is based on the testimony of Zacharias Janssen's son, Johannes Zachariassen, who may have fabricated the whole story ([[#Van Helden|Van Helden]], p. 43).</ref> pushes the invention date so far back that Zacharias would have been a child at the time, leading to speculation that, for Johannes' claim to be true, the compound microscope would have to have been invented by Johannes' grandfather, Hans Martens.<ref name=Shmaefsky/> Another claim is that Janssen's competitor, [[Hans Lippershey]] (who applied for the first telescope patent in 1608) also invented the compound microscope.<ref>{{cite web|url=http://www.livescience.com/39649-who-invented-the-microscope.html|title=Who Invented the Microscope?|website=[[Live Science]] |date=14 September 2013 |access-date=31 March 2017|url-status=live|archive-url=https://web.archive.org/web/20170203052525/http://www.livescience.com/39649-who-invented-the-microscope.html|archive-date=3 February 2017}}</ref> Other historians point to the Dutch innovator Cornelis Drebbel with his 1621 compound microscope.<ref name="Raymond J. Seeger 2016, page 24"/><ref name="J. William Rosenthal 1996, page 391"/>

[[Galileo Galilei]] is sometimes cited as a compound microscope inventor. After 1610, he found that he could close focus his telescope to view small objects, such as flies, close up<ref>Robert D. Huerta, Giants of Delft: Johannes Vermeer and the Natural Philosophers : the Parallel Search for Knowledge During the Age of Discovery, Bucknell University Press - 2003, page 126</ref> and/or could look through the wrong end in reverse to magnify small objects.<ref>A. Mark Smith, From Sight to Light: The Passage from Ancient to Modern Optics, University of Chicago Press - 2014, page 387</ref> The only drawback was that his 2 foot long telescope had to be extended out to 6 feet to view objects that close.<ref>Daniel J. Boorstin, The Discoverers, Knopf Doubleday Publishing Group - 2011, page 327</ref> After seeing the compound microscope built by  Drebbel exhibited in Rome in 1624, Galileo built his own improved version.<ref name="Raymond J. Seeger 2016, page 24"/><ref name="J. William Rosenthal 1996, page 391"/> In 1625, [[Giovanni Faber]] coined the name ''microscope'' for the compound microscope Galileo submitted to the {{lang|it|[[Accademia dei Lincei]]|italic=no}} in 1624 <ref>{{cite book |author=Gould, Stephen Jay |title=The Lying Stones of Marrakech: Penultimate Reflections in Natural History |url=https://archive.org/details/isbn_9780095031417 |url-access=registration | chapter = Chapter 2: The Sharp-Eyed Lynx, Outfoxed by Nature |publisher=Harmony |location=New York, N.Y |year=2000 |isbn=978-0-224-05044-9}}</ref> (Galileo had called it the "''occhiolino''" or "''little eye''"). Faber coined the name from the [[Greek language|Greek]] words ''μικρόν'' (micron) meaning "small", and ''σκοπεῖν'' (skopein) meaning "to look at", a name meant to be analogous with "telescope", another word coined by the Linceans.<ref>[http://brunelleschi.imss.fi.it/esplora/microscopio/dswmedia/risorse/testi_completi.pdf "Il microscopio di Galileo"] {{webarchive|url=https://web.archive.org/web/20080409010159/http://brunelleschi.imss.fi.it/esplora/microscopio/dswmedia/risorse/testi_completi.pdf |date=9 April 2008 }}, Instituto e Museo di Storia della Scienza (in Italian)</ref>

[[Christiaan Huygens]], another Dutchman, developed a simple 2-lens ocular system in the late 17th century that was [[Achromatic lens|achromatically]] corrected, and therefore a huge step forward in microscope development. The Huygens ocular is still being produced to this day, but suffers from a small field size, and other minor disadvantages.{{cn|date=December 2024}}

===Popularization===
[[File:Stelluti bees1630.jpg|thumb|right|The oldest published image known to have been made with a microscope: bees by [[Francesco Stelluti]], 1630<ref>Gould, Stephen Jay (2000) ''[[The Lying Stones of Marrakech]]''. Harmony Books. {{ISBN|0-609-60142-3}}.</ref>]]
[[Antonie van Leeuwenhoek]] (1632–1724) is credited with bringing the microscope to the attention of biologists, even though simple magnifying lenses were already being produced in the 16th century. Van Leeuwenhoek's home-made microscopes were simple microscopes, with a single very small, yet strong lens. They were awkward in use, but enabled van Leeuwenhoek to see detailed images. It took about 150 years of optical development before the compound microscope was able to provide the same quality image as van Leeuwenhoek's simple microscopes, due to difficulties in configuring multiple lenses. In the 1850s, [[John Leonard Riddell]], Professor of Chemistry at [[Tulane University]], invented the first practical binocular microscope while carrying out one of the earliest and most extensive American microscopic investigations of [[cholera]].<ref name="Riddell">{{cite journal | author = Riddell JL | title = On the binocular microscope | journal = Q J Microsc Sci | volume = 2 | pages = 18–24 | year = 1854}}</ref><ref name="Cassedy">{{cite journal | author = Cassedy JH | title = John L. Riddell's Vibrio biceps: Two documents on American microscopy and cholera etiology 1849–59 | journal = J Hist Med | volume = 28 | pages = 101–108 | year = 1973 | issue=2| doi = 10.1093/jhmas/xxviii.2.101 | pmid = 4572620 }}</ref>

===Lighting techniques===
While basic microscope technology and optics have been available for over 400 years it is much more recently that techniques in sample illumination were developed to generate the high quality images seen today.{{Citation needed|date=August 2024}}

In August 1893, [[August Köhler]] developed [[Köhler illumination]]. This method of sample illumination gives rise to extremely even lighting and overcomes many limitations of older techniques of sample illumination. Before development of Köhler illumination the image of the light source, for example a [[lightbulb]] filament, was always visible in the image of the sample.{{Citation needed|date=August 2024}}

The [[Nobel Prize]] in physics was awarded to Dutch physicist [[Frits Zernike]] in 1953 for his development of [[phase contrast]] illumination which allows imaging of transparent samples. By using [[Interference (wave propagation)|interference]] rather than [[Absorption (electromagnetic radiation)|absorption]] of light, extremely transparent samples, such as live [[mammalian]] cells, can be imaged without having to use staining techniques. Just two years later, in 1955, [[Georges Nomarski]] published the theory for [[differential interference contrast]] microscopy, another [[Interference (wave propagation)|interference]]-based imaging technique.{{Citation needed|date=August 2024}}

===Fluorescence microscopy===
Modern biological microscopy depends heavily on the development of [[fluorescent]] [[Hybridization probe|probe]]s for specific structures within a cell. In contrast to normal transilluminated light microscopy, in [[fluorescence microscopy]] the sample is illuminated through the objective lens with a narrow set of wavelengths of light. This light interacts with fluorophores in the sample which then emit light of a longer [[wavelength]]. It is this emitted light which makes up the image.{{cn|date=December 2024}}

Since the mid-20th century chemical fluorescent stains, such as [[DAPI]] which binds to [[DNA]], have been used to label specific structures within the cell. More recent developments include [[immunofluorescence]], which uses fluorescently labelled [[antibodies]] to recognise specific proteins within a sample, and fluorescent proteins like [[Green fluorescent protein|GFP]] which a live cell can [[gene expression|express]] making it fluorescent.{{cn|date=December 2024}}