 The present review outlines recent progress in the study of exosomes, which are nanosized biovesicles released by cells that carry cell-specific cargos and can be taken up by neighboring or distant cells to reprogram them. Exosome research is focused on understanding their regulatory mechanisms, molecular composition, and potential users' diagnostic and therapeutic biomarkers and vehicles for drug and gene delivery. Further in-depth study of subcellular components and mechanisms involved in exosome formation and specific cell targeting will shed light on their physiological activities. This article was offered by Yuan Zhong, Yunfeng Liu, Haiying Liu, and others.