Ionic liquids (IL) exhibit a remarkably diverse interfacial chemistry, with multiple interfacial layers present at the IL/solid interface. Ionic liquids (ILs) are pure salts with melting points typically less than 100°C. It has remarkable physical properties, which include wide electrochemical stability windows, high ionic conductivity and negligible vapor pressure. The adsorption strength of ILs onto solid surfaces is much higher than for typical organic solvents or water. The structure and composition of the interfacial layer can be tuned by varying the surface potential and the ionic structure, and by addition of solutes. This allows us to envision that IL interfacial properties can be readily matched to a particular application once the required fundamental understanding is elucidated. STM and AFM results show that the IL cation has a strong influence on the structure and composition of the interface.