The basics of electromagnetic (EM) interaction with materials were elucidated over a century ago and stated as the well-known Maxwell’s equations. The application of these basics to biological systems, however, is very diffi cult because of the extreme complexity and multiple levels of organization in living organisms, in addition to the wide range of electrical properties of biological tissues. The above diffi culty has slowed the progress of understanding the EM bioeffects. Yet knowledge of the interaction mechanisms could be utilized to identify appropriate dosimetry, to predict dose-response relationships, to design better experiments, and to assist in determining whether harmful effects are likely at specifi c levels of exposure.