Superionic solids are a new emerging area of materials science, as these solids show a tremendous technological scope for developing a wide variety of solid-state electrochemical devices such as batteries, fuel cells, supercapacitors, sensors, electrochromic displays (ECDs), memories, etc. These devices have a wide range of applicabilities, viz. power sources for IC microchips to transport vehicles, novel sensors for controlling atmospheric pollution, new kinds of memory for computers, smart windows/ display panels, etc. At the present time,"nanoionics" are drawing considerable attention worldwide as it is expected that this novel phase of solid-state ionic materials will involve new phenomena/effects akin to nanoscience/nanotechnology, which is currently one of the most sought after frontline research areas. This chapter explains the synthesis and characterization routes of different superionic solids in various phases. Ion conduction phenomenon and device fabrications are also presented.