According to the preservation needs of medicines, reagents and various biological agents, refrigerators with different temperature control levels must be provided, and the most commonly used refrigerators are: 4 ℃,-20 ℃ and-80 ℃. 4 ℃ is suitable for storing some solutions, reagents, medicines, etc. -20 ℃ is suitable for some reagents, drugs, enzymes, serum, prepared antibiotics, DNA and protein samples, etc. -80 ℃ is suitable for the preservation of some samples stored at low temperature for a long time, purified samples and special digestive juice treated at low temperature. The freezer at 0-10 ℃ is suitable for electrophoresis, chromatography, dialysis and other experiments at low temperature.