In this book, the authors intended to focus their effort on describing (1) biological responses of human and animals, both in vivo and in vitro methodologies, to magnetic and/or electromagnetic field exposure, (2) characteristics of effective fields, (3) hypotheses to explain possible mechanisms of interaction between the fields and cells, and (4) induced current in ELF and induced heat in RF fields as key interaction mechanisms. The readers can have the present-day comprehensive knowledge about biological responses to electromagnetic field exposure.