THE SCIENCE:
Since adult stem cells are rare, scientists may be able to use tissue that is more easily available, such as the skin. In one method, researchers replace the genetic material from a donor egg with the nucleus of a skin cell; the new hybrid begins to grow like an embryo from which stem cells can be isolated. These in turn could produce transplants that are immunologically identical to the original host and therefore won't be rejected.
THE ETHICS:
The technique is similar to that used to clone embryos, which led the House last week to vote against any research using this procedure.