This chapter introduces the fundamental concepts of thermal comfort and physiological thermoregulation as well as the importance of clothing thermoregulation. It reviews the history and recent progress of clothing for passive and active thermoregulation. A detailed classification of thermoregulatory clothing with cooling or heating effect is provided based on the components and working mechanisms. Also, various textile materials and garment designs are discussed and compared in efficiency, usability, safety, and cost. These comparisons allow researchers to determine the advantages and disadvantages of each thermoregulating approach and make a selection for a specific situation.