This ovum is in a primary follicle in an ovary removed from a 42-year-old woman with a benign ovarian cyst.

Baby girls are born with all the ova they will ever produce, popping out one (and occasionally two) every 28 days from puberty until menopause. When it's time for the egg's great adventure, the ovarian tissue that encases the anointed egg proliferates and becomes differentiated into granulosa and theca cells, producing the much larger, cystic Graafian follicle. When mature, the follicle ruptures, and the egg explodes from the torn surface of the ovary (occasionally producing a pain called "mittelschmerz") and is swept up into the nearby fallopian tube, where, if sperm make the rendezvouz, it is fertlized and converted into a zygote that begins dividing. This early embryo continues its way down the tube and into the uterus, where it implants itself and develops into a baby.

400X, Hematoxylin and eosin.