Recently the generation of human embryonic stem cells(hESCs) and induced pluripotent stem cells (iPSCs) have provided novel strategies to derive patient—specific pluripolent stem cells. hESCs and hiPSCs are unique pluripolcnt stem cells that are characterized by the capability of unlimited self-renewal. Under appropriate niche environment, these stem cells can develop into all cell lineages (including germ cells. eggs and sperm) in the human body.