In order to discover ways to cure diseases, studies on therapeutic approaches have expanded widely and continued to develop at an accelerated pace. Many areas of research have emerged with this goal in mind, including one of the most fascinating and active areas today, stem cell therapies. Due to the self-renewal property and differentiation ability of stem cells, they become a new hope in modern treatment. The first successful case of stem cell therapy in humans was reported in 1959. Bone marrow restorations were observed in leukemia patients who received total body irradiation. then by intravenous injection of the bone marrow of their twins (Thomas et al, 1957). Nevertheless, this effect was transient and subsequent attempts at bone marrow transplantation in non-twin patients and donors may eventually lead to patient death from graft-versus-host disease (Mathé et al, 1965). At that time, the safety of hematopoietic cell transplantation was not guaranteed due to limited knowledge of human histocompatibility and immunosuppression. However, the turning point came after the discovery of human leukocyte antigen (HLA) groups (Dausset, 1958; van Rood et al, 1958), HLA typing and compatibility testing were performed before transplantation. Furthermore, improvement in the immunosuppressive protocol also contributes to bone marrow transplantation becoming increasingly successful (Donnall and Hutchinson, 1999). Although the success rate of hematopoietic stem cell therapy was high, patient mortality persisted due to certain factors. In addition to the previously mentioned graft-versus-host disease, infection contributes to most cases of patient death (Kernan et al, 1993). In the allogeneic field... middle of article...... there are certain risk factors associated with the use of stem cells for therapeutic approaches, hematopoietic stem cell therapy through bone marrow transplantation is is already proven safe if donor history and screening, cellular contamination, HLA matching, and opportunistic or nosocomial infections during the immunocompromised period have been carefully monitored and controlled. Yet other types of stem cell therapies, despite their good therapeutic efficacy, remain at the experimental stage and require more data to support and demonstrate their safety in clinical trials. A better understanding of stem cell biology is also necessary in order to keep stem cells under control and avoid certain complications they could cause. Thus, to pave the way for successful stem cell therapy, research to this extent is necessary to maximize therapeutic efficacy with utmost safety in patients..