Cryopreservation is a process where cells or whole tissues are preserved by cooling to sub-zero temperatures, typically 77 K (= ?196 °C, the boiling point of liquid nitrogen). At these cold temperatures, any biological activity, including the biochemical reactions that would cause cell death, is effectively stopped. However, if cryoprotectant solutions are not used, the cells being preserved are likely to be damaged due to freezing during the cooling or thawing process.