Stem cells are a kind of master cell for the body. Depending on their source, they have the ability to produce many different kinds of cells. So far scientists cannot control this process but are learning to do so and they hope to use them to produce tissues for transplant and perhaps even entire organs. Adult stem cells have been found in the bone marrow, the blood, the brain, liver and other parts of the body and give rise to specific families of cells. Some research suggests that they, too, may be re-programmed to some degree so that blood stem cells could, for instance, produce nerve cells.
Scientists say research needs to proceed on both kinds of cells.
We may be on the cusp of a new era of medicine, one in which cell therapy could restore normal function to a variety of affected tissues. But Kansas Republican Sam Brownback said he did not consider it moral to trade one human life for another, and he considers the embryos to be human lives. He supports, instead, research using adult stem cells.