Two phenomena which cause damage to cells during cryopreservation are solution effects and intracellular ice formation. Solution effects are caused by concentration of solutes in non-frozen solution during freezing. The mechanism of cell damage due to intracellular ice formation is not well understood.
[Water bear]?s (or tardigrada?), microscopic multicellular organisms, can survive freezing at low temperatures by replacing most of their internal water with the sugar trehalose?.