Gene banks use low temperatures to stop chemical and biological activity that might break down cells. Some banks freeze material in liquid nitrogen at –196° Celsius (-320.8° Fahrenheit). This freezing process replaces water in cells with another fluid, such as glycerol. That fluid minimizes the development of ice crystals. Such crystals could damage cell walls. Later, during thawing, biologists will remove the glycerol or some other fluid and return water to the cells.