"Unlike men, who produce new sperm daily throughout most of their lifetime, women are born with all their eggs in one — okay, two baskets (ovaries). To be more precise, a woman is born with about one to two million immature eggs, or follicles, in her ovaries.
Throughout her life, the vast majority of follicles will die through a process known as atresia. Atresia begins at birth and continues throughout the course of the woman’s reproductive life. When a woman reaches puberty and starts to menstruate, only about 400,000 follicles remain. With each menstrual cycle, a thousand follicles are lost and only one lucky little follicle will actually **mature into an ovum (egg), **which is released into the fallopian tube, kicking off ovulation. That means that of the one to two million follicles, only
about 400 will ever mature."