Hematoxylin (Hematoxylin) and Eosin (Eosin) co-staining referred to as HE staining is one of the most commonly used staining methods in pathology and histology. Hematoxylin is an alkaline natural dye that can color the cell nucleus. The main component of chromatin in the cell nucleus is DNA, and in the double helix structure of DNA, the phosphate groups on the two nucleotide chains are outwardly oriented, which makes the outside of the DNA double helix negatively charged and acidic, and it can easily be stained by combining with the positively charged Hematoxylin alkaline dye by ionic bonding or hydrogen bonding.

Heidenhain Iron Hematoxylin Staining Solution uses ammonium iron sulfate as oxidizing and differentiating agent, which can show different structures according to different different degrees of differentiation, and all components are black or dark gray-black after staining. Hematoxylin staining of different tissue structures can be faded out by Heidenhain Differentiation Solution at different rates of progressive fading, and the order of fading out of the black color is in the following order: mitochondria, transversus muscle, and nuclear chromatin.