A Drosophila ovary consists of a bundle of ovarioles, each of which contains a progression of oogenesis stages, from the anterior to the posterior. The anterior region is called the germarium. Germline stem cells in the germarium divide to produce primary oogonia, which in turn undergo four mitotic divisions to generate a 16-cell cyst. One of these becomes the oocyte and the other 15 become nurse cells. Immediately after the final division, premeiotic S phase, zygotene, and pachytene ensue. During pachytene, meiotic recombination takes place.

At the posterior end of the germarium, each cyst becomes encapsulated by somatic follicle cells, and enters the region known as the vitellarium. This region consists mostly of oocyte growth and development. Over a period of serveral days, the nurse cells synthesize mRNAs and proteins, which eventually get dumped into the oocyte to support embryonic development.