What is the temperature of a cryostat?

• A. -20 C
• B. 37 C
• C. 4 C
• D. -70 C

Answer: (A)

A cryostat is used for freezing tissue so you can cut thin frozen sections, and the temperature must keep the tissue safely frozen yet workable for microtomy. Setting the chamber around -20°C is the standard because it freezes the tissue quickly enough to preserve morphology and prevent thawing, while still allowing the blade to cut cleanly without excessive brittleness. This balance gives consistent, crisp sections for staining and examination.

If you store or work at 37°C, the tissue would thaw and lose structure, making sections useless. At 4°C, the tissue remains cold but unfrozen, leading to soft, smeared sections and potential partial thawing. Going as cold as -70°C is usually too extreme for routine cryostat cutting; it can make tissue too brittle and stress the instrument. So, -20°C is the typical and most practical setting for a cryostat.