The exsosomes contain structures of protein, mRNA, microRNA, etc., which are wrapped in a nanosized lipid bilayer of 30-100 nm diameter. Exosomes exist naturally in body fluids, such as blood, saliva, urine, breast milk. Exosomes are secreted from active cells and are membrane vesicles derived from late endosomes (also referred to as polycysts). Almost all kinds of cells, including tumor cells, can generate and secrete exosomes. The exsosomes are secreted from the cells and released into the body fluid, eventually taken into other cells. This is an important mediator of intercellular communication.