Exosomes are nanoscale extracellular vesicles (EVs) released by cells into the extracellular environment, typically ranging from 30–150 nm in diameter. They are enclosed by a lipid bilayer and contain a variety of biologically active molecules, including proteins, lipids, mRNAs, miRNAs, and other biomolecules. Exosomes play important roles in intercellular communication, molecular transport, and the regulation of various biological processes.

Exosomes can be secreted by a wide range of cell types, including mesenchymal stem cells (MSCs), immune cells, tumor cells, and epithelial cells. Owing to their naturally derived lipid membrane, diverse molecular cargo, and ability to mediate intercellular communication, exosomes have been widely studied in cell communication, disease mechanism research, biomarker discovery, drug delivery, and regenerative medicine.