The lecture will start with the overview of the researches after 1980 which undoubtedly proved the presence of ion channels/receptors by elucidating the molecular identity. Then, the molecular and functional diversity of ion channels/receptors will be explained. The lecturer will then explain the mechanisms and structural determinants of ion channel functions, focusing on the ionic selectivity and the voltage-dependent gating. Finally, various inherited diseases caused by genetic mutations of ion channel genes will be briefly introduced.