It takes about 2 weeks for a follicle to form into a mature follicle, and a mature follicle is formed and expelled about 2 weeks after menstruation. Follicles are born as primordial follicles and are present in a woman’s ovaries. 700,000-2,000,000 primordial follicles are present in a woman’s ovaries after birth, and the number of primordial follicles decreases during puberty, at about 40,000 follicles. During each menstrual cycle, a follicle develops and matures on one side of the ovary. There are generally 3 stages to go through, primordial follicles, growing follicles and mature follicles. Multiple primordial follicles begin to develop at the start of menstruation, only 1-2 dominant follicles exist when development enters the second stage, and only one mature follicle matures and ovulates during the mature stage, so follicles can develop and mature over a 2-week period of the menstrual cycle.