Amyloid is an amorphous extracellular eosinophilic substance that can exist in different tissues and organs， leading to diseases called amyloidosis.Amyloids are mainly composed of proteins， most of which are arranged in reverse beta folded layer structures. Under an electron microscope， amyloid like substances are arranged in a fibrillar pattern， and in the case material， there are a large number of extracellular， unbranched filaments， mostly randomly arranged.

Special staining methods used to identify amyloid substances include methyl violet staining， Congo red staining， and polarized light microscopy observation. This kit uses fluorescence staining method， which is based on the principle that Thioflavin T (ThT) is a benzothiazole dye that exhibits enhanced fluorescence when bound to amyloid fibrils and A β protein， thereby localizing and staining amyloid protein.