In cases where a surplus of eggs or embryos requires safe storage, cryopreservation answers the need. The most modern form of cryopreservation is vitrification, a ‘flash-freeze’ technique that employs liquid nitrogen to lower the temperature of the egg or embryo at a highly accelerated rate. And speed is important here, because it prevents the formation of ice crystals that can damage the delicate tissues being frozen. Following vitrification, embryos and eggs are kept at a temperature of -196°C in a medium of liquid nitrogen and may be stored for up to 13 years. Embryos thus preserved demonstrate a post-thaw survival rate of 95%, while also retaining the youthful appearance of fresh embryos.