Ovulation: false-colour scanning electron micrograph showing the release of a mature ovum (Graafian follicle) at ovulation. The ovum (red) is surrounded by remnants of corona cells & liquid liquori folliculi from the ruptured ovarian follicle. Mature ova develop in the ovaries from primordial follicles which, although formed during foetal development, remain dormant until sexual maturity. In each ovarian cycle up to 20 primordial follicles are activated to form primary follicles; normally only one attains maturity, forming the Graafian follicle that ruptures at ovulation. Magnification: x72 at 6x7cm size. Similar (cropped version) of Plate 47, Viaggio""