Abstract: A brief overview is given of several types of thermoelectric materials, including the standard Bi2Te3, PbTe and SiGe, common structures such as the skutterudites, clathrates, half-Heusler intermetallic compounds, metal oxides and Zn4Sb3-type compounds, as well as types with various new crystal structures. The crystal structure and optimization of the thermoelectric properties of these materials are discussed.