An engaging introduction to stem cells for young scientists How do you heal when you cut your skin or break a bone? How does your body keep making new blood or brain cells, or even second teeth? How does a plant keep growing larger? The answers lie in stem cells, which are found in every growing plant and animal. Keeping the subject simple enough for young readers, a pioneer of stem cell research explains cells, tissues, normal growth, what can go wrong, and how to fix it.