(The Center Square) – Girls are born with a million small structures called primordial follicles. Each of these contains an egg cell. As girls grow and develop, most of these follicles die, and each month, just one follicle typically ovulates a mature egg.

“When the loss of primordial follicles is nearly complete, and only hundreds remain, women experience menopause, a time when menstrual cycles have ceased for 12 months,” a release from the University of Utah said.