Hematoxylin (Hematoxylin) and Eosin (Eosin) combined staining referred to as HE staining, is a commonly used staining method in pathology and histology. Hematoxylin is an alkaline natural dye, which 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 outer side of the double helix of DNA negatively charged and acidic, which can easily be stained with the positively charged Hematoxylin alkaline dye by combining with ionic bonding or hydrogen bonding.