This book explores intrinsic and human body part biometrics and biometrics of human physiological activities, invisible to the naked eye. This includes, for instance, brain structures, skeleton morphology, heart activity, etc. These human body parts can only be visualized using specific imaging techniques or sensors, commonly employed in the biomedical engineering field. As such, the book connects two fields, namely biometric security and biomedical engineering. The book is suitable for advanced graduate and postgraduate students, engineers and researchers, especially in Signal and Image Processing, Biometrics, and Biomedical Engineering.