What is stem cell therapy (regenerative medicine), and how does it work? Content What are stem cells? Why is there such an interest in stem cells? Where do stem cells come from? Why is there a controversy about using embryonic stem cells? Where do these embryos come from? Why can't researchers use adult stem cells instead? What are stem cell lines and why do researchers want to use them? What is stem cell therapy (regenerative medicine) and how does it work? Have stem cells already been used to treat diseases? What are the potential problems with using embryonic stem cells in humans? What is therapeutic cloning, and what benefits might it offer? Has therapeutic cloning in people been successful?