Eggs, zoologically, are referred to as OVA. OVA are the reproductive cells of female animals, and they are typically larger than the male reproductive cells, known as sperm. In many species, OVA are released from the female's body and fertilized by sperm in the environment. The resulting embryo is then nurtured by the female until it hatches. OVA are also used in some forms of artificial reproduction, such as in vitro fertilization.