The so-called reticulocytes are red blood cells that have not yet fully matured. Its value in the surrounding blood can reflect the production function of bone marrow red blood cells for the diagnosis and curative effect observation of blood diseases. The proliferation and development of red blood cells in the bone marrow: pluripotent stem cells→unipotent stem cells→primordial red blood cells→premature red blood cells→mesoblasts→late red blood cells→reticulocytes→mature red blood cells. From the proliferation of primitive red blood cells to the stage of late immature red blood cells, it divides 3-4 times. It takes about 72 hours. The number of red blood cells changes from one to 8-16. The nucleus changes from large to small and concentrated, and the hemoglobin in the cytoplasm gradually increases. The cells no longer divide after the late erythrocytes, and the nucleus is expelled during development and becomes reticulocytes. Reticulocytes contain a small amount of ribonucleic acid (RNA), which form a network when stained with brilliant tar blue, hence the name reticulocytes. Reticulocytes mature further, RNA disappears and become mature red blood cells. It takes about 48 hours to develop from late immature red blood cells to mature red blood cells. Under normal circumstances, nucleated red blood cells in the bone marrow are not released into the blood circulation. Only reticulocytes and mature red blood cells are released into the blood. Therefore, by checking the number of reticulocytes in the peripheral blood, it can be inferred that the bone marrow produces red blood cells. The six parameters of reticulocytes include the total number of reticulocytes (Retic#), the percentage of reticulocytes (Retic%), the average volume of reticulocytes (MCVr), the average hemoglobin concentration of a single reticulocyte (CHCMr), and the distribution of reticulocytes. Width (RDWr), single reticulocyte hemoglobin content (CHr), etc., among which the most significant, in addition to the total number, percentage, the most important reticulocyte hemoglobin content (CHr) parameters. Increased clinical significance of reticulocytes: ① It suggests that bone marrow hematopoietic function is exuberant, such as iron deficiency anemia, megaloblastic (folic acid, vitamin B12) anemia, hemorrhagic anemia, especially hemolytic anemia. Significant, often> 10%. ②After iron deficiency anemia and megaloblastic anemia were treated with iron, vitamin B12, and folic acid, reticulocytes increased significantly. reduction: suggests that bone marrow hematopoietic function is low, which is seen in aplastic anemia and acute leukemia. Anemia does not show hyperplasia, it may be severe aplastic anemia. A significant increase after anti-anemia treatment indicates that the treatment is effective, and vice versa.