Editing Microscope (section)

===Optical microscope===
{{main|Optical microscope|Digital microscope|USB microscope}}
The most common type of microscope (and the first invented) is the [[optical microscope]]. This is an [[optics|optical]] [[measuring instrument|instrument]] containing one or more [[Lens (optics)|lenses]] producing an enlarged image of a sample placed in the focal plane. Optical microscopes have [[refraction|refractive]] glass (occasionally plastic or [[quartz]]), to focus light on the eye or on to another light detector. Mirror-based optical microscopes operate in the same manner. Typical magnification of a light microscope, assuming visible range light, is up to 1,250× with a theoretical [[Diffraction-limited system|resolution limit]] of around 0.250&nbsp;[[micrometre]]s or 250&nbsp;[[nanometre]]s.<ref name=":0"/> This limits practical magnification to ~1,500×. Specialized techniques (e.g., [[Confocal laser scanning microscopy|scanning confocal microscopy]], [[Vertico SMI]]) may exceed this magnification but the resolution is [[diffraction]] limited. The use of shorter wavelengths of light, such as ultraviolet, is one way to improve the spatial resolution of the optical microscope, as are devices such as the [[near-field scanning optical microscope]].

[[Sarfus]] is a recent optical technique that increases the sensitivity of a standard optical microscope to a point where it is possible to directly visualize nanometric films (down to 0.3&nbsp;nanometre) and isolated nano-objects (down to 2&nbsp;nm-diameter). The technique is based on the use of non-reflecting substrates for cross-polarized reflected light microscopy.

[[Ultraviolet]] light enables the resolution of microscopic features as well as the imaging of samples that are transparent to the eye. [[Near infrared]] light can be used to visualize circuitry embedded in bonded silicon devices, since silicon is transparent in this region of wavelengths.

In [[fluorescence microscopy]] many wavelengths of light ranging from the ultraviolet to the visible can be used to cause samples to [[fluorescence|fluoresce]], which allows viewing by eye or with specifically sensitive cameras.[[File:Brightfield phase contrast cell image.jpg|thumb|Unstained cells viewed by typical brightfield (left) compared to phase-contrast microscopy (right)]]

[[Phase-contrast microscopy]] is an [[optical microscope|optical microscopic]] illumination technique in which small [[phase shifts]] in the light passing through a transparent specimen are converted into [[amplitude]] or [[contrast (vision)|contrast]] changes in the image.<ref name=":0"/> The use of phase contrast does not require [[staining]] to view the slide. This microscope technique made it possible to study the [[cell cycle]] in live cells.

The traditional optical microscope has more recently evolved into the [[digital microscope]]. In addition to, or instead of, directly viewing the object through the [[eyepiece]]s, a type of sensor similar to those used in a [[digital camera]] is used to obtain an image, which is then displayed on a computer monitor. These sensors may use [[CMOS]] or [[charge-coupled device]] (CCD) technology, depending on the application.

Digital microscopy with very low light levels to avoid damage to vulnerable biological samples is available using sensitive [[photon counting|photon-counting]] digital cameras. It has been demonstrated that a light source providing pairs of [[Photon entanglement|entangled photons]] may minimize the risk of damage to the most light-sensitive samples. In this application of [[ghost imaging]] to photon-sparse microscopy, the sample is illuminated with infrared photons, each of which is spatially correlated with an entangled partner in the visible band for efficient imaging by a photon-counting camera.<ref name="AspdenGemmell2015">{{cite journal|last1=Aspden|first1=Reuben S. |last2=Gemmell|first2=Nathan R. |last3=Morris|first3=Peter A. |last4=Tasca|first4=Daniel S. |last5=Mertens|first5=Lena |last6=Tanner|first6=Michael G. |last7=Kirkwood|first7=Robert A. |last8=Ruggeri|first8=Alessandro |last9=Tosi|first9=Alberto |last10=Boyd|first10=Robert W. |last11=Buller|first11=Gerald S. |last12=Hadfield |first12=Robert H. |last13=Padgett |first13=Miles J. |title=Photon-sparse microscopy: visible light imaging using infrared illumination |journal=Optica |volume=2 |issue=12 |year=2015 |pages=1049 |issn=2334-2536 |doi=10.1364/OPTICA.2.001049|bibcode=2015Optic...2.1049A |url=http://eprints.gla.ac.uk/112219/1/112219.pdf |doi-access=free }}</ref>
[[File:Electron Microscope.jpg|thumb|upright|Modern transmission electron microscope]]