The study of the effect of low temperatures (below the freezing point of water) on biological systems. A primary goal of this field is the preservation and long term storage of organ systems such as hearts, kidneys, etc. for use in transplantation. This goal has not yet been reached and currently only individual cells and organisms consisting of only a very few cells (such as embryos) can be successfully treated, stored, and revived. See cryopreservation.