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 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 or hydrogen bonding. The methods of maturation of hematoxylin are natural oxidation and chemical oxidation; natural oxidation means exposure to light and air, the 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 of; hematoxylin staining solution (Ehrich's) is used as a good nuclear staining solution, but also can be used for mucus Hematoxylin Stain (Ehrich's) is recommended for staining proteins such as mucopolysaccharides of cartilage, and for staining bone and cartilage.

Hematoxylin staining solution (Ehrich's) is very stable, can be stored for 2 years after maturation and sealed, the nuclear chromatin staining is very clear and detailed, the staining time is also a little longer, about 15-20min, suitable for teaching and scientific research on the preparation of staining, with this staining solution for frozen section staining is not ideal.