Embryo freezing begins with hormone medication, injected over for 8–12 days, that stimulates the ovaries to produce multiple eggs. Once mature, the eggs are collected from the ovaries via an egg retrieval procedure. Sperm from a male partner or sperm donor is prepared through a process called “sperm washing,” which isolates healthy sperm to improve the chances of fertilization. The sperm is then combined with the egg in the laboratory (known as in vitro fertilization) to create embryos. The embryos develop for approximately 5 days under close monitoring by embryologists, and finally, they’re vitrified (flash frozen). Just as with eggs, once frozen, embryos remain as healthy and high quality as they were when they were created.