Cryopreservation of Mammalian Embryos by Vitrification

protectant for spermatozoa41) led to research on cryopreservation of mammalian embryos. In the past quarter of a century since the first successful cryopreservation of mouse embryos58,60), basic and applied research has resulted in the cryopreservation of embryos of many mammalian species. Improvements have been made in nearly all steps of the cryopreservation process, resulting in considerable simplification of the original slow freezing and thawing procedures. Recently, the first successful cryopreservation of murine embryos by vitrification was reported by Rall and Fahy43). Using highly concentrated solutions of cryoprotectants, they obtained high survival rates of mouse