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 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. The methods of hematoxylin maturation are natural oxidation and chemical oxidation. Natural oxidation refers to exposure to light and air, this process is slow, ranging from about 3 to 6 months, but the staining ability of the product can be maintained for a very long time, Ehrlich and Delafield hematoxylin belongs to this kind.

Delafield hematoxylin staining solution is very stable, after maturation and sealing can be stored for 2 years, on the nuclear chromatin staining is very clear and detailed, staining time is also a little longer, about 15 to 20min, suitable for teaching and scientific research on the preparation of staining, with this staining solution on the frozen section staining is not ideal.