In most female mammals, the migration of primordial germ cells, germ cells meiosis, and breakdown of germ cell nests are regarded as the 3 critical processes for the formation of early primordial follicles. In addition, there are some special factors and signaling pathways regulating the formation and development of primordial follicles. However, the reproductive ability of a female is determined by the size and reserve capacity of her primordial follicle pool. This review summarizes the factors and signaling pathways involved in the formation and development of primordial follicles, with the ...