This review of heat and mass transfer in biological systems is focused on phenomena occurring at low temperatures at the micro- and nano-scales. The discussed temperature range is divided into temperatures above freezing and temperatures below freeing. At temperatures above freezing, the effects of low temperature relate to changes in the molecular structure of cell membranes, changes in ionic pump function, and chemical reaction kinetics. Below freezing, processes relate to water transport across cell membranes and changes in intracellular composition. The mechanisms through which organisms survive changes induced by low temperatures are also discussed together with biomedical applications of low temperatures in cryopreservation of organs for transplantation and destruction of undesirable tissues by freezing in cryosurgery.