Extracellular vesicles are mainly composed of microvesicles, apoptotic vesicles, and exosomes. They have a double-layer membrane structure and are shed from cell membranes or secreted by cells. As one type of small vesicle with a diameter of 40~100 nm and a density of 1.10~1.18 g/ml, exosomes can carry nucleic acid, protein mass and lipids. and exist in various body fluids such as blood, saliva and urine. Exosomes can affect cell functions by transferring substances such as nucleic acids, proteins and lipids between cells. For example, they play an essential role in antigen presentation in antigen-presenting cells, in the development of tumour cells, and in signal transduction in nerve cells. The detection and analysis of exosomes can accelerate disease-related basic research, and assist in disease diagnosis, drug development, therapeutic research, and drug efficacy evaluation.