What is Cryo-Electron Microscopy (Cryo-EM)?

Transmission Electron Microscopes (TEM) transmit a beam of electrons through a sample to create an image. While the electrons pass through the sample, some will be scattered by heavier atoms in the sample creating a projection image. Imaging of biological material with EM requires protection of the sample from the high vacuum conditions and the intense beam of electrons. The electrons transfer a high amount of energy into the sample that destroys the structure while the vacuum causes the water that surrounds the molecules to evaporate. A way to protect the sample from these extreme conditions is cryogenics. By rapidly freezing, the sample is vitrified and adopts a glass-like state, without formation of ice crystals. In this state the sample deteriorates much slower, allowing the study of biological material using TEM.

source Delmic