Originally Posted by MSN.COM

In one technique, scientists would harvest viable cells from embryos created to treat infertility but which have stopped developing and are functionally dead. Taking the cells — which can grow into stem cells — would be analogous to removing organs of brain-dead accident victims for transplant.

In the second technique, scientists would intentionally sabotage a cloning process called "nuclear transfer" so that the resulting bundle of cells is not an embryo but still has stem cell precursors. They could then be removed and used.