What Stem Cells Can Do
Stem cells are undifferentiated or partially differentiated cells that can self-renew and produce specialized cells. However, not all are precursors of every cell in the human body. Human embryonic stem cells are pluripotent and can give rise to nearly all body cell types; tissue (adult) stem cells are usually limited to a particular tissue or lineage—for example, blood-forming stem cells produce blood cells.
Self-renewal means that, during division, a stem cell can maintain its own pool while also producing daughter cells that begin to differentiate. Potency varies among stem-cell types: pluripotency is not a property of every stem cell.