Extracellular vesicles (EVs) are particles of varying size, structure, and composition, which are secreted from cells and frequently mediate intercellular communication. Because they have been shown to travel through the circulatory system and also through biological barriers to deliver their molecular contents to distant target cells, there has been growing interest in using EVs, such as exosomes, as drug delivery vehicles. In the past ten years, the number of published articles linking EVs to drug delivery has increased 20-fold. EVs are being engineered to deliver protein, RNA, and small molecule cargo to target cells, tissues, and entire systems. Also, EVs derived from certain cells show inherent, therapeutically beneficial activity.