In comparison to conventional solvents, deep eutectic solvents (DESs) provide several benefits over those employed in a variety of chemical and biological processes. DESs, depending on their nature, can not only address most of the principles of green chemistry, but they can also operate as catalysts in various processes. The use of DESs has several advantages, including the ability to be used in a stoichiometric amount, nontoxicity, the possibility of recovery, and the ability to be recycled and reused without experiencing a significant loss of activity. Because of their wide range of applications since their first publication in the literature in 2003, they have attracted considerable attention. These include selective biomass or metal extraction for pharmaceuticals, pollution control systems, and catalytic active solvents and co-solvents. It is possible to take advantage of the extremely distinctive DES physical features, such as increased density and viscosity, decreased conductivity, and enhanced solubility, as well as unusual optical behavior, to engineer highly modular systems that are not possible with other non-eutectic substances. The chapter reviews the manner the DESs are being used in the synthesis of process materials, as solvents for volatile organic compounds, as active agents and ingredients in drug substances and co-solvents in organic synthesis, and what the future holds for these fields. This chapter focuses on recent research efforts to elucidate the next stages necessary to establish a basic framework for a deeper knowledge of DESs, as well as the next steps required to develop a fundamental framework.