What is a Graafian Follicle? Ovarian follicles are the essential units of female reproductive biology, each of which is packed with roughly spherical aggregations of cells found in the ovary. A Graafian follicle, or ovarian follicle, is present inside an ovary and is a minute cyst within which an egg, or ovum, develops. A Graafian follicle is a follicle that ruptures and releases its ovum when stimulated. Generally, women are born with many undeveloped follicles, each containing an immature ovum.