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 nucleus of cells; the main component of chromatin in the nucleus of the cell is DNA, and in the double-helix structure of the DNA, the phosphate groups on the two nucleotide chains are outwardly oriented, so that the outer side of the double helix of DNA is negatively charged and acidic. In the double helix structure of DNA, the phosphate groups on the two nucleotide chains are directed outward, so that the outer side of the DNA double helix is negatively charged and acidic, and it can easily be stained with the positively charged hematoxylin alkaline dyes by ionic or hydrogen bonds.