This review volume will present the latest progress on the application of terahertz (THz) spectroscopy in Physics, Chemistry, Material Science and Engineering. It will showcase the ever-expanding use of this frequency region in understanding the development of photonic devices in the THz frequencies as well as advances in the emission and detection of THz pulses. This book is intended for Masters, PhD and post-graduate researchers anticipating a career in linear and non-linear spectroscopy and/or in the development of THz devices and techniques.