Hematoxylin (Hematoxylin) and Eosin (Eosin) combined staining referred to as HE staining, is the most 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, and it can easily be stained by combining with the positively charged Hematoxylin alkaline dye by ionic bonding or hydrogen bonding.