Embryonic stem cells are derived from embryos and can be described as the master cells of the human body. Not only can they self-renew, they can develop into just about any type of cell, even in a fully grown body. In contrast, adult stem cells can renew, but can’t generate beyond their tissue types. For example, an adult heart cell cannot become a brain cell. While embryonic stem cell harvesting is controversial, the thought is that stem cell therapy offers significant potential for regenerating diseased or damaged tissues, offering hope for treating conditions such as Alzheimer’s, heart diseases or spinal cord injuries.