Exosomes: biogenesis, function and clinical potential About Exosomes: Exosomes are small (30-100 nm) biovesicles which are released by all kind of cells into body fluids like blood and urine. In the beginning they thought to be waste resulting from cell damage or by-products of cell homeostasis but recent studies show that they have an important role in intercellular communication through their cargo which may play a role in processes such as signal transduction, antigen presentation and immune response.