A primordial follicle can spend years in "quiescence" until it initiates its development. Subsequently, once initiated, it takes approximately 150 days for a primordial follicle to become a Graafian follicle. This means that the follicle that will ovulate in a given menstrual cycle began to develop about 5 menstrual cycles earlier, along with many other follicles that have been lost during their development due to atresia.