Cell cryopreservation is one of the main methods of cell preservation. Using cryopreservation technology to store cells in liquid nitrogen at -196°C can temporarily detach cells from their growth state and preserve their cell characteristics, so that cells can be revived for experiments when needed. Moreover, appropriately preserving a certain amount of cells can prevent cells from being lost due to contamination of the cultured cells or other accidents, thus playing the role of cell species preservation. In addition, certain cells can also be purchased, donated, exchanged and transported in the form of cell cryopreservation. When freezing cells, add a protective agent to the culture medium - the final concentration is 5%. 15% glycerol or dimethyl sulfoxide (DMSO) can lower the freezing point of the solution. In addition, under slow freezing conditions, intracellular water leaks out, reducing the formation of ice crystals and thus avoiding cell damage. The method of slow freezing and quick thawing can better ensure the survival of cells. The standard freezing speed starts from -1 to -2℃/min. It can be accelerated when the temperature is lower than -25℃. After reaching -80℃, it can be directly put into liquid nitrogen (-196℃).