Vitrification is ultra rapid embryo freezing instead of the traditional slow freezing process. Vitrification is the process of converting something into glass like solid that is free of any crystal formation. Vitrification can be used for preserving the oocytes for fertility preservation. Vitrification can allow freezing of spare embryos with better post- thaw survival rates and higher pregnancy and live birth rates from frozen embryo transfer cycles. Embryos can be frozen at the pronuclear stage (one cell), or at any stage after that up to including blastocyst stage (5-7days after fertilization). Different cryoprotectants and freezing solutions can be used for different stages of embryo development.