The polychromatophilic normoblasts represent the maturation stage between basophilic and orthochromatic normoblasts in the maturation cascade of erythropoiesis. They constitute about of nucleated bone marrow cells (myelogram). Hemoglobin synthesis begins to change the cytoplasmic color more acidophilic.
The polychromatic normoblasts are smaller (diameter of 10-12 µm) than the basophilic normoblasts. The nucleus is smaller and more compact. The cytoplasm is in transition from basophilic to acidophilic; hence the term polychromatophilic. They are often found in groups.