Basic and clinical research on adult stem cells is progressing rapidly. New technology that can generate iPS (induced pluripotent stem cells) cells from various types of tissue may completely change the stem cell world and regenerative medicine. In terms of clinical applications, both bone marrow and skin are very attractive sources of adult stem cells because they are highly accessible and the procedures to obtain them are minimally invasive. However, we have to seriously consider both safety issues and cost performance when we treat patients with cultured cells. We should use animal-free materials as often as possible and remember that culture stressors may induce epigenetic changes in the cultured cells. Nonetheless, there can be no doubt that stem-cell-based therapy is a promising tool in the field of regenerative medicine.