It's about meiosis...?

Meiosis is how both eggs and sperm are created. The end result in both is half of the male's (for sperm) or female's (for eggs) DNA which is 23 chromosomes. The joining comes from ual reproduction. In the case of people, when the sperm and egg join then the resulting cell has the full 46 chromosomes needed for sapiens. Meiosis only happens in ovaries, before the female is even born, and in testes of men from puberty till death.