Cryopreservation involves freezing and storing biological materials at extremely low temperatures. The first documented cryopreservation was of sperm in 1760, but the most significant discovery was the use of glycerol as a cryoprotectant in 1949. Cryopreservation works through three steps - freezing, storing, and thawing - and allows for the long-term availability and preservation of materials important for assisted reproduction like sperm and embryos.