Currently, solid state (ceramic) ion conductors are being considered to replace conventional liquid and gel electrolytes in numerous electrochemical energy technologies such as batteries due to their high voltage and chemical-thermal stabilities. There are several family of inorganic crystalline and amorphous compounds discovered as fast ion conductors since 1950. However, their application in modern devices are limited today. Only a few solid ion conductors have been used in commercial electrochemical technologies. This talk will report milestones in solid state ionics, including Professors Huggins’s key contributions.