Egg cells
The egg is a germ cell of a female animal. Egg cells (produced by secondary oocytes) become mature after becoming an egg. In mammals, the eggs are produced by the ovaries. All mammals at birth, the ovaries have immature eggs present, and the number of eggs after birth will not increase. Egg and sperm combined with fertilization will form fertilized eggs, that is, the beginning of a new life. Some animals (such as birds) are in vivo fertilized, while others (such as most of the fish and amphibians) are in vitro fertilization. ...