Atom tunneling phenomena are a new paradigm in the science of materials. This book provides a wealth of interesting information about atom tunneling phenomena in physics, chemistry and biology. Topics include the theory of atom tunneling reactions, conclusive evidence and controlling factors for such reactions in solid hydrogen, tunneling dislocation motion, coherent tunneling diffusion, the production of interstellar molecules and semiconductors using tunneling reactions, the effect of atom tunneling on molecular structure and crystalline structure, the suppression of mutation and cancer by an atom tunneling reaction of vitamin C, and atom tunneling reactions of vitamin E and of enzymes. This book provides graduate students and nonspecialist readers with fascinating insights into the world of atom tunneling phenomena.