Of the estimated trillion cells that build up our bodies, only a little number can self-renew and give rise to many different cell types. These unspecialized cells are called stem cells. Stem cell division and differentiation is fundamental to the development of the mature organism. Stem cells have recently attracted significant attention largely due to their potential medical benefits in the fields of therapeutic cloning and regenerative medicine. Because stem cells can become many specialized types of cells of the organs, they have the potential to treat many diseases, including Alzheimer's disease, Parkinson's disease, type-1 diabetes, spinal cord injury, stroke, burns, heart disease, osteoarthritis, and rheumatoid arthritis. This book focuses on the application of stem cells in regeneration and repair of the organs in disease and aging.