This book provides a clearly structured introduction to hydrogen biology and medicine. Hydrogen is the one of the most abundant elements in the universe and has the simplest structure. In 2007, Japanese researchers found that the selective oxidation of hydrogen has a therapeutic effect on various diseases and injuries, sparking widespread interest in the biomedical field. In recent years, hundreds of peer-reviewed papers have been published internationally reporting the positive effects of hydrogen on many human diseases, including strokes, diabetes, Parkinson's disease, Alzheimer's disease and sepsis. The authors provide readers with a comprehensive overview of this subject, from its physical and chemical properties to its biological effects, as well as the problems and obstacles that exist.