Stem cells. Coloured scanning electron micrograph (SEM) of stem cells taken from umbilical cord blood. These cells are known as multipotent because they undergo differentiation to produce precursors of all the body's specialised blood cells. By this process, termed haemopoiesis, stem cells develop either into red blood cells, or one of several types of white blood cells that make up the immune system. The purification of stem cells from umbilical cord blood allows scientists to research the function of the immune system and to develop treatments for diseases such as AIDS and leukaemia. Magnification unknown.