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Cryo microscopy is a technique where a microscope is equipped such that the object to inspected can be cooled below room temperature. Technically, cryo microscopy implies compatibility between a cryostat and the microscope. Most cryostat's are making use of a cryogenic fluid such a liquid helium or liquid nitrogen. There exist at least two motivations for cryo microscopy. One is to improve the microscopy. Cryogenic electron microscopy, for example, enables to study proteins with limited radiation damage. Here the protein structure may not change with temperature, but the cryogenic environment enables improved electron microscopy. Another motivation is to apply microscopy to a low temperature phenomenon. Scanning tunnelling microscopy under cryogenic environment, for example, allows to study superconductivity that does not exist at room temperature.

History
Although optical microscopes have existed for centuries, cryo microscopy is a modern methodology. In the 1950'ties, ice crystal s were studied by installing an electron microscope inside an igloo. Around 1980, adaption of electron microscope, vacuum and cryostat led to the beginning of modern cryo microscopy. This development of cryo electron microscopy was awarded the 2017 chemistry Nobel Prize to Jacques Dubochet, Joachim Frank and Richard Henderson.

Cryogenic electron microscopy
Main article: Cryogenic electron microscopy

Scanning or transmission electron microscopy carried out under cryogenic condition is known as cryoSEM and cryoTEM, respectively.

Cryogenic optical microscopy
Cryogenic environment is used in combination with different types of optical microscopy techniques. Growth of artificial ice crystals are for example studied by optical microscopy. With polarized light microscopy, birefringence effect from for example orthorhombic domain structures can be observed at cryogenic temperatures. In life science, fluorescence microscopy has enabled resolution beyond the diffraction limit. The Nobel Prize in Chemistry 2014 was jointly awarded to Eric Betzig, Stefan Hell, and William E. Moerner "for the development of super-resolved fluorescence microscopy". Cryogenic environment minimize bleaching which in turn improve the contrast of the microscopy technique.