In this chapter, we have reviewed the current state of the knowledge of the ionic liquid-solid interface, which is vital for applications and whose studies are still in its infancy. Emphasis has been placed on atomic or molecular-resolution characterization by scanning tunneling microscopy (STM). Firstly, technological point of STM for ionic liquids (ILs) has been briefly discussed. Secondly, updated researches on the adsorption behavior of anions and cations of ILs are exploited. Thirdly, potentials of ILs in metal deposition are reviewed. Fourthly, potentials of ILs in deposition of elemental and compound semiconductors are discussed. Finally, applications of ILs in deposition of organic molecules are briefly discussed. We conclude this chapter with personal perspectives on the directions to which future research on this field might be directed.