Cryo-scanning electron microscope (Cryo-SEM)
Cryo stands for frozen. A cryo-scanning electron microscope is a conventional SEM that has been fitted with specific equipment that allows samples to be viewed in the frozen state. This is particularly useful for directly viewing hydrated (wet) samples, delicate biological samples, hydrogels, food, biofilms, foams, fats, and waxes, suspensions, pharmaceuticals and nanoparticles. The sample can be snap frozen outside the machine and then inserted in its frozen state, or placed into the machine in an unfrozen state and frozen more slowly in the machine. It is imaged using either secondary electrons (SE) or backscattered electrons (BSE). Frozen samples can also be fractured or cut during preparation to reveal internal structures.