Received August 10, 2007
Accepted September 25, 2007

Classic methods of cryopreservation of biological specimens allow the formation of ice crystals inside the cells, which most of the times are deleterious for cell survival. Vitrification, where the high rate of cooling is combined with high concentrations of cryoprotectants, does not allow the formation of ice crystals during cooling or warming. Several improvements on the methodology are being tested for the successful vitrification of human embryos and oocytes, but the survival rates and embryo development post-warming have been very variable among different laboratories due, most likely, to the lack of consistency in the methodology employed. On the other hand, successful reports each time more frequent from a few groups, give strong evidences that vitrification shall occupy a prominent place in human cryobiology.