Table 1.

EV classification and biogenic mechanisms.

	Exosomes (EXOs)	Microvesicles (MVs)	Apoptotic Bodies (ABs)
Diameter (nm)	30–150	100–1000	100–5000
Biogenesis	Budding from endosome lumen (Figure 2B)	Budding from the plasma membrane (Figure 2C)	Released during apoptosis (Figure 2D)
Biogenesis Steps	Endocytic materials are internalized and stored in early endosomes; During the maturation of early endosomes in late endosomes, molecules are sorted into intraluminal vesicles (ILVs) with the aid of the ESCRT complexes; Late endosomes can be degraded or fuse with the plasma membrane and release their content, the EXOs, in the extracellular milieu.	The plasma membrane is actively maintained in a state of asymmetry in terms of lipid composition; Calcium-dependent membrane proteins alter the membrane asymmetry leading to the loss of membrane–cytoskeletal anchorage and the formation of regions prone to form blebs; MVs bud from the plasma membrane via ESCRT machinery or through the activation of the ARF6.	Cellular stress, infection, or DNA damage can trigger apoptosis; During apoptosis, a cell undergoes cytoskeleton disruption, nuclear fragmentation, and membrane blebbing releasing ABs; Clearance of apoptotic cells or ABs is operated by professional phagocytes or by neigh-boring cells.