Generation of a mature oocyte from a preantral ovine follicle. The preantral follicle was isolated from the ovary and photographed after 6, 13 and 20 days of culture. Antrum formation was clearly observed from Day 13 onwards. The oocyte with surrounding somatic cells was extracted from the follicle and resumed meiosis up to the Metaphase II (MII) stage on the next day. Scale bar: 100 µm.