Amyloid is an extracellular eosinophilic substance without a fixed shape, which can be present in different tissues and organs, resulting in a disease called amyloidosis; amyloid is mainly composed of proteins, most of which are arranged in an inverted β-folded lamellar structure. Under the electron microscope, amyloid is arranged in protofibrils, which in the case material are large numbers of extracellular, unbranched filaments, mostly randomly arranged. The histological methods used to identify amyloid are methyl violet staining, Congo red staining, polarized light microscope observation, etc. Current research has found that the traditional methyl violet staining method has low sensitivity and poor specificity, and the classic and effective method is Congo red staining. 1922 Bennhold found that Congo red could be used for the identification of amyloid in vivo, and it was applied to the tissue sections, which was later improved by Highman. Highman improved it for better staining.

Amyloid staining solution (methyl violet method) mainly consists of methyl violet staining solution and acidic differentiation solution, which is a heterochromatic staining solution improved by Jurgens, and its staining principle is that acidic mucopolysaccharides in the proteoids react heterochromatically with methyl violet, and the advantage of which is that it is convenient and time-saving, and the disadvantage is that it is difficult to preserve the sections after staining.