Stem cells are undifferentiated cells characterized by self renewal, multipotency, long term tissue repopulation after transplantation, serial transplant ability and when divide the daughter cell can either fully differentiated or remain stem cell. Haematopoietic stem cells can be differentiated into hepatocytes, cardiomyocytes, brain cells, hair follicles and sebaceous glands, epithelial and nonepithelital cell types in the kidney, islet cells in pancreas, type II pneumocytes in the lungs, mucous secreting cells in the stomach, goblet cells and enteroendocrine cells in the intestine. For treatment of genetic diseases, transplantation of genetically modified autologous marrow would avoid many of the risks of allogerric transplants. It is used in treatment of many diseases as cystic fibrosis, Duchenne muscular dystrophy, immunodeficiency diseases, some types of anemias like thalassemia and sickle cell anemia and wound healing, gasterointestinal diseases and autoimmune diseases. Hepatocyte transplantations have been performed for a variety of indications, including inborn errors of metabolism. Cells derived from other tissues, such as bone marrow, monocytes, endothelium, and pancreas, are also being explored as potential therapies for liver based metabolic disorders.Stem cells are not only units of biological organization, responsible for the development and the regeneration of tissue and organ systems, but are also targets of carcinogenesis. Bone marrow stem cells can be used to accelerate liver regeneration before extended hepatectomy for hepatocellular carcinoma.