In recent years, novel families of materials have been discovered and significant improvements in classical thermoelectric materials have been made. Thermoelectric generators are now being used to harvest industrial heat waste and convert it into electricity. This is being utilized in communal incinerators, large smelters, and cement plants. Leading car and truck companies are developing thermoelectric power generators to collect heat from the exhaust systems of gasoline and diesel engines. Additionally, thermoelectric coolers are being used in a variety of picnic boxes, vessels used to transport transplant organs, and in air-conditioned seats of mid-size cars. Consisting of twenty-one chapters written by top researchers in the field, this book explores the major advancements being made in the material aspects of thermoelectricity and provides a critical assessment in regards to the broadening of application opportunities for thermoelectric energy conversion.