The naturally occurring dye hematoxylin stains acidic (basophilic) structures blue; in particular, cell nuclei and DNA contained therein, as well as the rough endoplasmic reticulum.

Mayer's hematoxylin acidic is a special histological staining method that uses Mayer's acidic hematoxylin to stain cell nuclei and other basophilic structures in tissue sections. Mayer hematoxylin is a modified version of the classic hematoxylin stain that uses aluminum ammonium sulfate to produce a more stable and less toxic solution. The acidic formulation of Mayer hematoxylin prevents the staining of erythrocytes, making the cell nuclei more visible. This staining method is often used in combination with eosin or other contrasting dyes to allow better differentiation of cell structures.