Peripheral blood is the blood in the terminal capillaries. The common clinical sites for obtaining peripheral blood are the ring finger and the earlobe. Generally speaking, the most common tests to obtain peripheral blood are routine blood tests, blood group tests and blood smear tests. However, because of the richness of peripheral nerves in the area of the ring finger, the patient sometimes suffers more pain when taking peripheral blood, especially in the abdomen of the ring finger, but for some pediatric patients, it is sometimes necessary to take peripheral blood because of the difficulty of taking blood from the elbow vein. In addition, if the blood type is simply done, it is sufficient to take peripheral blood. Also, in the hematology department, peripheral blood is often taken for a blood smear, which is done under a microscope to see if the cells have a normal shape.