The ever-growing interest in exosomes research is mainly due to their potential applications in health and disease, especially in therapy and diagnosis. To explore the applications of exosomes in the clinical setting, we must understand their characteristics at the molecular levels. Furthermore, exosomes are cell and function specific; therefore, we must ascertain the molecular mechanisms of their biogenesis, cellular recognition, and uptake. In the recent past, engineered exosomes and exosome mimetics have been the subject of active research. However, critical facets of the biology of engineered exosomes and exosome mimetics remain unknown. This review presents our current understanding of the potential role of engineered exosomes and exosome mimetics in diagnosis, prognosis, monitoring of treatment, as well as drug delivery. We also present recent updates on the exosome signature, its role in pancreatic cancer progression, and applications in the delivery of natural therapeutics and RNAi molecules and in the immune response. Lastly, we discuss future prospects and challenges of exosomes in translational studies.