When your skin is cut, it heals. When you break a bone, it mends. How does this happen? Because your body is made of cells, including a very special kind called stem cells. They live in many places in your body, such as skin, muscles, bones, and blood. And when any part of your body is injured, stem cells jump into action to repair the damage. This book contains a tale told in rhyme about how stem cells work and what scientists are doing to help them work even better, especially as people get older.