This book is one of the first to apply engineering science and technology to biological cells and tissues that are electrically conducting and excitable. It describes the theory and a wide range of applications in both electric and magnetic fields. The similarities and differences between bioelectricity and biomagnetism are described in detail from the viewpoint of lead field theory. This book will enable readers to understand the properties of existing bioelectric and biomagnetic measurements and stimulation methods, and to design new systems. It includes carefully drawn illustrations and 500 references, and can be used as a textbook and as a reference.