Transient receptor potential (TRP) channels are involved in the perception of a wide range of physical and chemical stimuli, including temperature and osmolarity changes, light, pain, touch, taste and pheromones, and in the initiation of cellular responses thereupon. Since the last decade, rapid progress has been made in the identification and characterization of new members of the TRP superfamily. They constitute a large superfamily of cation channels that are expressed in almost all cell types in both invertebrates and vertebrates. This review summarizes and discusses the current knowledge on the TRP protein structure and its impact on the regulation of the channel function.