Cloning is done with progenitor cells. A stem cell can replicate into two cells, another stem cell and a progenitor cell. This progenitor cell then becomes other cells such as muscle, bone, fat, and white blood cells. In culture, stem cells can reproduce indefinitely. Researchers have learned to use retroviruses to create induced pluripotent stem cells by inducing master regulatory genes. These genes were introduced to a skin fibroblast progenitor cell and it became a stem cell. These induced pluripotent stem cells are not the same as embryonic stem cells but can perform most of the same functions. This research seems to be the most ethical way to "clone" a cell. This research would be able to be used to create more red and white blood cells for medical purposes, lowering the amount of blood needed too be donated by people. This type of replication isn't really cloning but imitation of stem cell behavior. Stem cells are necessary for human health and any way to get them would benefit the population as a whole immensely.