The state of the art in stem cell biology and regenerative medicine: the end of the beginning.

With translational stem cell biology and Regenerative Medicine (the field to which the former gave rise) now over a quarter century old, it is time to take stock of where we have been and where we are going. This editorial overview, which serves as an introduction to this special issue of Pediatric Research dedicated to these fields, reinforces the notion that stem cells are ultimately intrinsic parts of developmental biology, for which Pediatrics represents the clinical face. Although stem cells provide the cellular basis for a great deal of only recently recognized plasticity programmed into the developing and postdevelopmental organism, and although there is enormous promise in harnessing this plasticity for therapeutic advantage, their successful use rests on a deep understanding of their developmental imperatives and the developmental programs in which they engage. The potential uses of stems are ranked and discussed in the order of most readily achievable to those requiring extensively more work. Although that order may not be what was contemplated at the field's birth, we nevertheless retain an optimism for the ultimate positive impact of exploiting this fundamental biology for the well-being of children.