Cell therapy has emerged as a strategy for the treatment of many human diseases. Because no single cell or universal donor is likely to be useful for all diseases, it is the source and the desired function of the cell that will dictate which cell type is most useful for each disease. Concerns related to immunological compatibility, ability to multiply cells in vitro before transplantation and general issues of quality control and safety are now being addressed by the convergence of disciplines interested in the potential for cell therapy.