Stem cells on the way to restorative medicine.

Stem cells are defined by their unique properties of self-renewal and multilineage differentiation. Several decades ago, cells with such developmental plasticity have been identified in the embryo and in the bone marrow of the adult; in other organs, such cells could not be demonstrated. Here, recent findings are briefly summarized indicating that the elementary stem cell capabilities are retained by a limited number of cells present in many organs of the adult. Other data suggest that, on response to another microenvironment, "organ-specific" stem cells are able to acquire different fates. If confirmed these findings will have considerable impact on the future of clinical stem cell therapy.