Stem cells are (pluripotent) undifferentiated cells that can differentiate into specialised cell types / tissues. Future medical uses involve growing organs from a patients OWN stem cells = zero chance of rejection and no shortages of organs. Stem cells can be found in the bone marrow, fat tissue and blood within an adult. Within fetus stem cells can be found within the umbilical cord and within the embryo. The latter source is controversial igniting debates on the sanity of life.