Atomic switch has a potential to achieve downscaling to smaller than the 11 nm technology node because of its unique operating mechanism. It also has novel characteristics, such as high on/off ratios, very low power consumption and non-volatility. In addition to the on/off bi-stable switching, the novel functions, such as synaptic, memristive, and photo-assisted operations, are demonstrated by two-terminal atomic switches. Three-terminal atomic switch shows volatile/nonvolatile dual functions. These novel functions will enable development of new type of electronic systems.