Cells are the basic units that constitute the basic structure and physiological functions of the human body, which is composed of a large number of cells. In the human body, except for mature red blood cells and platelets, cells have a nucleus structure and the human body is composed of different cells in different organs, for example, there are three types of blood cells in the human body, namely, red blood cells, white blood cells and platelets. Each type of cell has a different morphology and performs different functions respectively. Red blood cells appear as a disc with concave sides and have a diameter of about 7.5 um. The function of red blood cells is to transport oxygen and carbon dioxide because they contain hemoglobin, which binds to oxygen and carbon dioxide and performs the role of transport. The other function of white blood cells is to perform immune functions. The most numerous white blood cells are neutrophils, which can engulf pathogenic microorganisms that invade the body. The main function of platelets is to stop bleeding, because platelets have a series of functions such as adhesion, aggregation, contraction and secretion, which play an important role in the process of stopping bleeding in the body.