This book discusses fundamentally new biomedical imaging methods, such as holography, holographic and resonant interferometry, and speckle optics. It focuses on the development of holographic interference microscopy and its use in the study of phase objects such as nerve and muscle fibers subjected to the influence of laser radiation, magnetic fields, and hyperbaric conditions. The book shows how the myelin sheath and even the axon itself exhibit waveguide properties, enabling a fresh new look at the mechanisms of information transmission in the human body.