Most stem cells reside in particular organs and tissues and give rise to a limited repertoire of cells. Stem cells in the bone marrow, for instance, only produce blood cells. There are stem cells in the crypts of the intestine that are dedicated to the production of intestinal cells. But embryonic stem cells, or ES cells, which arise from the inner sheath of an animal’s embryo, are vastly more potent; they can give rise to every cell type in the organism—blood, brains, intestines, muscles, bone, skin. Biologists use the word pluripotent to describe this property of ES cells.
