Human embryonic stem cells (hESC) are harvested from the inner cell mass of the pre-implantation embryo and possess several unique characteristics. First, they are self-renewing, meaning they can grow indefinitely in an appropriate culture environment and secondly, they are pluripotent, which means they have the potential to become nearly every cell of the human body. Consequently, hESC offer a unique insight into basic human development in vitro, allow better understanding of the genetic and molecular controls of these processes, and are of pharmaceutical interest to test or develop new drugs. The most exciting and high-profile potential application of hESC research is the possibility that such cells can be used for regenerative medicine. Still, several obstacles have to be overcome before clinical applications can be considered: (i) xeno-free derivation and culture of hESC is necessary; (ii) hESC should be safe after transplantation and (iii) their identity and behaviour should be well-known
