FIGURE 1.

Formation of primordial follicles. Primordial germ cells (PGCs) migrate to the gonadal ridge (A) and form nests of oogonia surrounded by somatic cells (B) within the presumptive ovary. Oogonia undergo a defined period of proliferation prior to entering meiosis and forming oocytes (C). Meiosis progresses to the diplotene stage of prophase I to form oocytes that are found at 16 weeks of gestation in the human fetal ovary. Oocytes establish connections with somatic cells (granulosa cells) to form primordial follicles (D). Image created with BioRender.com, with permission.