The present invention is directed to a cryoprotective system that comprises an aqueous solution containing polymeric nano- and micro-particles that exhibit a reversible temperature-dependent volume change. It is also directed to a method for providing cryoprotection to an organism or parts of an organism by pumping the cryoprotective system into the vasculature of the organism prior to exposing the organism to a lower, preferably below 0 C., temperature.