Extracellular vesicles (EVs) are a part of the armamentarium that are poised to revolutionise precision medicine. Drawing from over 30 years of research, we have described how these small, yet robust particles are synthesised, classified and isolated from a range of cell types and biofluids. We have also described their physiological and pathological roles, which underscore their diagnostic and therapeutic potential. We explain that the molecular cargo of EVs is dynamic and provides a real-time snapshot of the cells from which they originate. While this offers a real opportunity in translational medicine, important biological and technical ramifications must be mitigated. We highlight key challenges in the field and offer our insight on potential solutions.