A stem cell is a kind of cells that has the capacity to renew itself and give rise to specialized cell types. Although other organ cells such as heart cells or liver cells are conducting a specific function, a stem cell is un commited and it remains uncommited untill it receives a signal to develop into a specialized cell.The process by which dividing ,unspecialized cells are equipped to perform spesific functions –muscle contraction or nevre cell communication ,for example is called differantiation .Their proliferative capacity combined with the ability to become specislized makes them unique. We know that stem cells,in various forms,can be obtained from the embryo,fetus and the adult.