Exosomes are membrane-bound nanovesicles that are typically 30–150 nm in size with various bioactive molecules. They are typically generated by first endocytosing various transmembrane proteins into endosomes within the cell, which are then sorted and form intraluminal vesicles. These vesicles are then released as the endosome merges with the cell membrane and releases its contents outside of the cell. Tetraspanins (CD9, CD63, CD81) are one of the most common proteins expressed on the surface of exosomes and are often used as exosome-specific markers. These proteins have been shown to interact with different proteins such as integrins and major histocompatibility complexes (MHC). Exosomes commonly act as carriers of genetic and proteomic information, and are therefore vital in intercellular communication. In its role as a cellular messenger, exosomes have been implicated in promoting cancer; because of this, they are also being investigated as potential therapeutic targets and delivery vehicles.