Bone marrow aspiration, which is a bone marrow aspiration test, is the most common test used in hematology to diagnose various hematologic disorders. The first thing that is done when bone marrow is drawn is a morphological examination of the bone marrow to see if the morphology and proportions of the various hematopoietic cells in the bone marrow are normal. Through morphological examination, it is possible to make a diagnosis of many diseases. For example, a severe decrease in various blood-forming cells in the bone marrow is most likely caused by aplastic anemia. If there is a large proliferation of infantile cells in the bone marrow, it is possible to diagnose acute leukemia. If there is an abnormal proliferation of plasma cells in the bone marrow, a plasma cell disease such as multiple myeloma can be considered. Of course, with the development of modern medicine, in addition to morphological examination, bone marrow aspiration can also be checked for immunology, molecular biology, cytogenetics, second-generation sequencing and other tests to make a more accurate diagnosis of hematologic diseases. Bone marrow morphological examination can also detect whether there are other sites of malignant tumors that have metastasized to the bone marrow.