At its very core, the exosome biogenesis pathway is relatively straightforward.
Exosome biogenesis begins after the invagination of the cell membrane. The inward budding of the cell membrane results in the formation of early endosomes.
In this pathway, the early endosomes eventually mature into late endosomes/multivesicular bodies (MVBs).
Within the MVBs, the exosomes originate as intraluminal vesicles (ILVs) (Image 1.1).
Exosomal biogenesis concludes when the MVB is transported to, and fuses with, the plasma membrane; whereupon the ILVs are released into the extracellular milieu.
Upon their release, the ILVs are then called exosomes.
Image 1.1: Exosome Biogenesis