Figure 4: Schematic view of recent progress in the study of in vitro spermatogenesis. In mice, PGC-like cells can be induced from ES and iPS cells under in vitro condition. Transplantation of PGC-like cells into the recipient mouse testis induces their differentiation up to sperm. On the other hand, SSCs can be induced to differentiate into sperm by organ culture in vitro (solid arrows). In future, a therapeutic strategy for infertile patients could be possible through same strategies, especially with in vitro culture method.