We are used to associate stem cells with renewable tissues such as blood, gut and skin. But some cells in the adult central nervous system have the capacity to generate new neurons and glial cells as well and as such, they are considered to be neural stem cell. Yet their ability to generate neurons and glia, and their presence in the central nervous system throughout life, suggests new, intriguing possibilities for recovery and repair after damage to the central nervous system--and unexpectedly, the regeneration of blood tissues. After transplantation into irradiated hosts, neural stem cells were found to produce a variety of blood cell types including myeloid and lymphoid cells as well as early hematopoietic cells. Therefore, the developmental potential of stem cells is not restricted to the differentiated elements of the tissue in which they reside. Multipotential stem cells can persist in an undifferentiated state, and depending on specific environmental conditions function as a stem cell for many different tissues.