The objective of this fourth volume in the series Advances in Electromagnetic Fields in Living Systems remains the same as previous volumes: to add a number of significant advances in this area of research to scientific and professional literature. In general, the interaction of electromagnetic fields and waves with biological systems is frequency-dependent. Moreover, the mechanisms of interaction for fields at low frequencies are very different from those at high frequencies. While significant advances are being made on many fronts, a special emphasis of this volume is on current and future biomedical applications of electromagnetic fields, ranging in frequency from quasi-static to the optical domain. Each chapter consists of a comprehensive presentation of a topic of current interest and growing importance.