This book presents physical models, backed by experimental results, explaining the behavior of living matter in relation to electromagnetic (EM) fields ranging from quasi-stationary state to optical range. The ability of very low frequency EM fields to cure diseases (e.g. respiratory infection) is addressed. The bacteria destruction by non-thermal effects of low frequency electric fields is explained with the proton nuclear resonance and the DNA half-wave resonance. The microtubule instabilities are studied. Explosion of bacteria with acoustic resonance is also modeled. Centimeter and millimeter-waves effects are discussed. Clues about interaction with the human brain are given. Effects of a 60 GHz field on cellular physiology are presented as well as on mice nerve system. A cell membrane is modeled in near IR to UV ranges. The capacity of cells to move towards an IR source is explained. Finally, explanation of cancer mechanisms of the human skin is proposed with ultra-weak photon energy.