Tetrachrome Stain (MacNeal) is primarily used in medical and biological laboratories for staining blood smears. It helps in the differentiation and identification of various blood cells, including red blood cells, white blood cells, and platelets. This stain is particularly useful in diagnosing blood disorders, infections, and other hematological conditions. It provides clear visualization of cell morphology, enabling pathologists to detect abnormalities such as anemia, leukemia, and parasitic infections like malaria. The stain is also employed in research settings to study blood cell characteristics and functions. Its application ensures accurate and detailed microscopic examination, aiding in both clinical diagnosis and scientific studies.