Germline stem cells (GSCs, green) and Escort Stem Cells (ESCs, orchid) reside at the anterior of a structure called the germarium. Asymmetric GSC divisions produce daughter cells that divide 4 times, producing a 16-cell cyst. The oocyte (OO, yellow) becomes specified, and the remaining 15 cells become nurse cells (NC, teal). Somatic stem cells (SSC, pink) reside halfway through the germarium. The daughter cells generated by asymmetric SSC division (pre-follicle cells (FC), red), extend processes that contact the cyst. Upon contact, FCs proliferate, invade, and surround the cyst, forming a FC-GC unit called an egg chamber.