 Stem cells have two features, self-renewal and multi-linage differentiation. Embryonic stem cells are associated with tumor genesis and ethical considerations, while adult mesenchymal stem cells are less problematic. MSCs can be isolated from various tissues and may be a good candidate for future experimental or clinical applications. The mechanisms of differentiation, mobilization, and homing of MSCs are complex, but their multipotent properties make them attractive for possible development of clinical applications. Future studies should explore the role of MSCs in differentiation, transplantation, and immune response in various diseases. This article was authored by Da Qingding, Weicheng Xu, and Xinzong Lin Md, Ph.D.