Embryo freezing, or cryopreservation, is the process of freezing embryos for future use. It is commonly done during in vitro fertilization (IVF) after embryos have developed to a suitable stage. Embryos are frozen in liquid nitrogen and can be stored for many years. This allows for multiple attempts at pregnancy without requiring additional egg retrievals. Frozen embryos can be thawed and transferred into the uterus in future IVF cycles, preserving fertility for women who want to delay pregnancy or for those with medical conditions affecting fertility. Embryo freezing also minimizes the risk of multiple pregnancies by enabling selective transfers.