Female: At birth, a girl's pair of ovaries contain up to 1,000,000 follicles, which are hollow balls of cells, each with an immature egg (or ovum) in the center. A girl is born with all the eggs ...

Throughout the follicular phase, a single "dominant follicle" develops faster than the rest. This follicle (a fluid-filled sac in your ovary) then releases more estrogen into the body in preparation ...