Cryopreservation of Mammalian Embryos: Vitrification

In 1972, Whittingham et al. (1 ) reported the first successful deepfreezing of mouse embryos. The method was efficient and reproducible, and it has been widely used since. This method includes a slow cooling process (this lasts a few hours after ice seeding). Recent attempts to improve the method have focused on shortening the cooling process. Vitrification, as reported by Rall and Fahy in 1985 (2 ), reduces the cooling stage duration to a minimum. Samples can be plunged directly into liquid nitrogen from temperatures above 0�C. An additional advantage of this approach is that high levels of viability of the embryos may be maintained; this is primarily attributed to the absence of extracellular ice during freezing.