Primary follicle consists of a primary oocyte which are in diakinesis stage of meiosis I surrounded by Granulosa cells. Theca develops around the follicle forming secondary follicle. Granulose cells secrete a fluid and create a cavity called antrum. Antrum containing follicle is called tertiary follicle. Meiosis I is completed. It produces secondary oocyte and a polar body. Follicle grows further and is called Graffian follicle. Zone pellucide develops around secondary oocyte which reaches up to metaphase II stage.