Electron cryomicroscopy is a form of electron microscopy (EM) where the sample is studied at cryo temperatures (generally liquid nitrogen temperatures). A version of Electron cryomicroscopy is Cryo Electron Tomography (CET) where a 3D reconstruction of a sample is created from tilted 2D images, again at cryo temperatures (either liquid nitrogen or helium). The electron microscope is a microscope that can magnify very small details with high resolving power due to the use of electrons rather than light to scatter off material, magnifying at levels up to 500,000 times. ...

Electron cryomicroscopy (aka cryoelectron microscopy) is a developing method in structural biology. Biology material are preserved in a frozen-hydrated state by rapid freezing, usually in liquid ethane near liquid nitrogen temperature. By maintaining specimens at liquid nitrogen temperature or colder, they can be introduced into the high-vacuum of the electron microscope column. Most biological specimens are extremely radiation sensitive, so they must be imaged with low-dose techniques. Consequently, the images are extremely noisy. The low temperature of electron cryomicroscopy provides an additional protective factor against radiation damage.

For some biological systems it is possible to average images to increase the signal to noise ratio and retrieve high-resolution information about the specimen. This approach requires that the things being averaged are identical (e.g. ribosome particles). Analysis of ordered arrays of protein, such as 2-D crystals of membrane proteins or helical arrays of proteins, also allows a kind of averaging which can provide high-resolution information about the specimen.