Despite recent astonishing advances in the treatment of infertility by assisted reproductive technology (ART), the fundamental approaches to solving complete infertility due to congenital absence of germ cells or impaired fertility arising from gonadotoxic therapies during prepubertal childhood still remain unclear. Current findings in stem cell biology have resulted in new possibilities for the treatment of reproductive diseases, i.e., germ cell formation may be inducible in vitro. The idea of generating artificial germ cells or gametes may lead to a solution for the treatment of infertility. In this article, we review the recent advances in research into formation of primordial germ cells (PGCs), which are the precursors of gametes, in vitro.