Ionic liquids are excellent substitutes for traditional organic solvents in many typical organic reactions, often producing higher selectivities as well as higher yields, and enhancing the reaction rate. Additionally, they can serve as catalyst immobilization for the easy recycling of homogeneous catalysts without need for special functionalization, and have been successfully employed as electrolytes in electrochemistry. "Tailor-made" solvents (optimization of the ionic liquid's characteristics) can be achieved through a broad choice of anion and cation combinations.