While sperm-making stem cells have been found in male testes, no one has ever found incontrovertible evidence for similar cells that make eggs in ovaries.

• 虽然人类已在雄性精巢内找到了能产生精子的干细胞，但还没有在卵巢内发现无可争议的、能够发育成卵子的类似细胞。