Abstract: A system is provided for selective clonogenic expansion of relatively undifferentiated cells, including (a) a tube containing a plurality of beads of a size which permits a plurality of the undifferentiated cells to grow thereon, the beads bearing on their surfaces a selective binding molecule which binds to a surface antigen present on the relatively undifferentiated cells, wherein the antigen is not present on the surfaces of the relatively differentiated cells; (b) means for continuously providing nutrients to the relatively undifferentiated cells growing on the beads, wherein the nutrients are delivered via a fluid which flows through the tube and past the beads; and (c) means for continuously harvesting the relatively undifferentiated cells downstream of the beads.