Deep eutectic solvents (DESs) and natural deep eutectic solvents (NADES) are gaining significant attention within the sample preparation field, particularly due to the unique physicochemical properties and environmentally friendly nature of these compounds. In addition to their sustainable aspects, the chemical stability and high efficiency to extract a wide range of analytes are valuable features that are being explored. In this chapter, a general overview of some fundamentals of sample preparation and applications of DES and NADES in extraction/microextraction approaches is provided and discussed. Some recent studies, particularly those reported in the last 5 years, are critically reviewed to provide a more complete understanding of the potential of these solvents in analytical extractions. Finally, trends in sample preparation techniques using DESs as extraction phases are pointed out and discussed.