Cryo-electron microscopy or cryo-EM examines frozen biological samples at cryogenic temperatures below −150 °C. Unlike conventional EM, cryo-EM does not require fixing and dehydrating a sample which helps to preserve the native state of biological structures. The high-energy electrons used in EM can damage a sample’s chemical bonds. Freezing the sample helps to prevent this damage, allowing for near atomic-resolution images. In cryo-EM, small biological samples in solution are vitrified, meaning rapidly frozen, in liquid ethane. Vitrification fixes the sample in its native state in a thin water layer, and the water in the sample forms a glass-like state without the appearance of ice crystals. Thicker samples, such as cells and tissues, cannot be vitrified in a thin liquid layer. Therefore, these samples can be studied using the cryo-EM of vitreous sections method. In this method, a sample is first vitrified by high-pressure freezing and then cut into ultrathin sections at −140 °C before being observed using cryo-EM.