Figure 1. Exosomes are composed of a lipid bilayer and a variety of molecules derived from their original cells such as miRNAs, mRNAs, and proteins.

Inside the cells, early endosomes are formed via endocytosis, early endosomes then develop to late endosomes, which form multivesicular bodies (MVBs) via the invagination of the membranes. The intraluminal vesicles (ILVs) are present in MVBs. Finally, MVBs fuse with the cell membrane and the ILVs will be released as exosomes.