Cryopreservation facilitates long-term storage of gametes and embryos for numerous purposes. For example, cryobanking of unique mouse strains, particularly transgenic mice, offers important protection of valuable genetics. It also provides a practical solution for facilities trying to house large numbers of research animals or those looking to relocate without the risk of introducing an animal-derived pathogen. Furthermore, cryopreservation is currently being used for fertility preservation both in humans and as a safeguard for endangered animals. Ultrarapid vitrification offers an elegant, quick, and very reliable method for cryopreservation of mouse oocytes and embryos. Furthermore, research into the effects on mouse oocyte and embryo physiology has indicated that ultrarapid vitrification is superior to conventional slow freezing. High survival rates, embryo development, and viability are routinely achieved with the ultrarapid vitrification method described in this chapter.