The energy of the nucleus can be tapped two ways: by splitting large nuclei into smaller ones (fission) or by combining small nuclei into larger ones (fusion). The first yields what we know as atomic or nuclear (fission) energy, together with its dangers and storage problems. The second gives fusion energy, which is basically solar power, since that is the way the sun and stars generate their energies. Fusion is much safer than fission and requires as fuel only a little bit of water (in the form of D2O instead of H2O, as will soon be clear). Fission is a well-developed technology, while fusion is still being perfected as an energy source. The object of this book is to show how far fusion research has gone, how much further there is to go, and what we will gain when we get there.