Stem cells build, maintain, and repair the body throughout our lives. Because these are processes that stem cells do naturally, they can be manipulated to repair damaged or diseased organs and tissues. But stem cells transferred from one person to another (such as in a bone marrow transplant) are seen as foreign, and they usually trigger an immune response.
Some researchers are looking at cloning as a way to create stem cells that are genetically identical to an individual. These cells could then beused for medical purposes, possibly even for growing whole organs. And stem cells cloned from someone with a disease could be grown in culture and studied to help researchers understand the disease and develop treatments.