This book is intended to serve as an in‎-depth analysis of thermoelectric theory‎,‎ an overview of present day thermoelectric materials and devices‎,‎ and as an updated source of information on the most studied recent thermoelectric materials developments‎.‎ The main emphasis is on a basic understanding of the concepts and experimental techniques needed to propel researchers towards new and novel classes of thermoelectric materials with enhanced properties‎.‎ The aim is to assist researchers in the field‎.‎ The text is an expanded edition of a previous text ‎"‎Electronic Refrigeration‎"‎ by one of the authors‎,‎ Julian Goldsmid‎.‎ Half of the text is devoted to research that has taken place since the publication of that text‎.‎ In addition‎,‎ emphasis is placed on new materials research and developments‎.‎