Ovary tissue. False-colour scanning electron micrograph (SEM) of cells in the corpus luteum. The corpus luteum develops after ovulation in the region of the ovary where the mature egg was released into the Fallopian tube. Luteal cells derive from follicular cells which, under the influence of the luteinizing hormone, increase their size and secrete a yellow pigment (lutein) and the progesterone hormone. The latter stimulates the uterine mucosa to enter the secretory stage which preceeds the implantation of the embryo. Magnification: x630 at 6x7cm size. x450 at 5x5cm