Identification of the stem and progenitor cells involved in generation or regeneration of a particular organ system or tissue concerns fairly rare populations. When one is dealing with regeneration of tissue or organ systems in a clinical circumstance where diseasesed or malignant cells may contaminate that organ system, practical regeneration can ocurr only if the stem/progenitor cells are purified nearly to homogeneity and do not contain contaminating diseased cells. To do this not only in animal models but in humans, one must be thinking of separation technologies that not only are high fidelity in terms of identifying and isolatin rare populations, but also are on a scale that is large enough to deliver adequate numbers of stem/progenitor cells for clinically effective and rapid regeneration. [Cell Separation Methods And Applications, New York, 1998]