The continuous effort to perform a more sustainable chemistry has led to the development of new materials that accomplish the principles of green chemistry. In this context, deep eutectic solvents (DESs) have arisen as a new generation of solvents that respond well to most of the characteristics that an ideal green solvent must possess: they are easy and cheap to prepare, stable, easy to handle (they show chemical stability, non-flammability and conductivity), separable from the reaction products, biodegradable and safe for both humans and the environment. At the same time, they show chemical-physical properties similar to ionic liquids, such as low volatility, conductivity and high solvent power. These characteristics mean that DESs are today classified as 2-st century solvents. DESs have been raising a lot of attention and a sharp increase of their applications in numerous sectors of chemistry: they are mainly used as alternative solvents and/or catalysts for various organic transformations including metal-catalyzed reactions, biotransformations, polymerization, in sample preparation and analytical techniques as well as in the design of pharmaceutical formulations and drug delivery systems.