This low magnification photomicrograph shows a bone marrow smear. This type of preparation allows for the examination of developing red and white cells. A marrow smear is made in a manner similar to that of a peripheral blood smear. A sample of bone marrow is aspirated from a bone and simply placed on a slide and spread into a thin monolayer of cells. A wide variety of cell types are present in the marrow smear. Most of the cells are developing granulocytes and developing erythrocytes. Mature erythrocytes (Ey) are also present in large numbers. They are readily identified by their lack of a nucleus and eosinophilic staining. Often intermixed with these red cells are small groups of reticulocytes. These are very young erythrocytes that  contain residual ribosomes in their cytoplasm. The presence of the ribosomes slightly alters the color of the reticulocyte giving it a just perceptible blue coloration in comparison to the mature eosinophilic erythrocyte. The reticulocytes are best distinguished at higher magnifications. In addition, adipocytes (A) are found in variable numbers. In preparations such as this, the lipid content is lost during preparation and recognition of the cell is based on a clear or unstained round space. Another large cell that is typically present is the megakaryocyte (M). The megakaryocyte is a polyploid cell that exhibits a large and irregular nuclear profile. It is the platelet-producing cell.
At this low magnification, it is difficult to distinguish the earlier stages of the developing cell types. However, examples of each stage of development in both cell lines are presented in the following plates. In contrast, many cells in their late stage of development, particularly in the granulocyte series, can be identified with some degree of assuredness at low magnification. For example, some band neutrophils (BN) and young eosinophils (E) can be identified by their morphology and staining characteristics.