Stem cells include in their progeny both more stem cells by self-renewal and mature cells by differentiation. Adult stem cells of one tissue type are restricted to produce cells of that type, and only the correct adult tissue stem cell will be useful in sustained regeneration of that tissue. For example, human blood-forming stem cells can generate all blood cell types in a mouse, and human brain-forming stem cells contribute appropriately to all brain cell types in the mouse brain. In contrast, in early fetal development, there are about 20 to 40 cells inside the blastocyst, at least some of which, at the single cell level, can contribute to the formation of all adult cell types. These are called pluripotent cells, from which it is possible to derive embryonic stem cell lines, and these can be used to learn much about human development and differentiation at a molecular and cellular level. The topics of this symposium include brain stem cells and the plasticity of neurons, recent advances in nuclear reprogramming of adult cells to create pluripotent stem cells, and cancer stem cells. It may be that only the cancer or leukemia stem cells are capable of self-renewal, and it is these cells that need to be understood at a molecular level, to develop the next generation of cancer therapeutics. The main focus of this symposium will be on the scientific advances in stem cell research and on the medical translations, but ethical and political issues will also be discussed.