Hematoxylin, a natural dye product, acts as a basic dye that stains blue or black. Nuclear heterochromatin stains blue and the cytoplasm of cells rich in ribonucleoprotein also stains blue. The cytoplasm of cells with minimal amounts of ribonucleoprotein tends to be lavender in color. The aniline dye, eosin, is an acid dye that stains cytoplasm, muscle, and connective tissues various shades of pink and orange. This difference in staining intensity is useful in differentiating one tissue from another.