Very broad potential application of cryopreserved oocytes in medicine (treatment of infertility , oocyte donation , etc.) , in veterinary medicine and animal husbandry (extension of genetic potential of females ) , ecology (creation of banks oocytes animal species threatened with extinction) and finally in doświadczalnictwie (eg the use of oocytes or cytoplastów cloning ) have until recently been restricted to the limited efficacy of cryopreservation methods . Cryopreservation methods used quite effectively to mouse oocytes , rabbit and to some extent against human oocytes proved to be of little use for cryopreservation of oocytes livestock . Especially subjected to intensive research over the last several years oocytes of cattle. However, regardless of the means of cryoprotectants and methods of cryopreservation (freezing or vitrification ) at best, only a few percent of oocytes that species evolved after fertilization in vitro to the blastocyst stage ( the development of control oocytes reaching the last even 35 ? 50%). Despite so the birth of several calves ( from 1992 onwards ? Initially only in Japan) , it was difficult to apply the method of oocyte cryopreservation of cattle considered effective. Breakthrough in mammalian oocyte cryopreservation methods brought called vitrification in samples with a minimum volume (minimum sample size) or more simply ? as the open method of vitrification . These methods are used today in several variants , have brought significant improvement of survival of oocytes and early embryos of cattle, pig and hamster embryos , and finally ? beginning to be applied to the cryopreservation of oocytes and embryos man.