Connective tissue is narrowly defined as the three types of fibers it contains: collagen fibers, reticular fibers, and elastin fibers, with collagen fibers (collagen fibers) being the most widely distributed and abundant type of fibers. masson's trichrome staining, also known as Masson staining, is one of the most classic methods of connective tissue staining, and it is the authoritative and classic technical method for staining collagen fibers. The so-called trichrome staining usually refers to staining the nucleus and can selectively display collagen fibers and myofibers, the staining principle of this method is related to the size of the anionic dye molecule and the penetration of the tissue: the size of the molecule is reflected by the molecular weight, small molecular weight is easy to penetrate the structure of dense, low permeability of the tissue; and the large molecular weight can only enter the structure of loose, high permeability of the tissue, however, the molecular weight of the light green or aniline blue are very large, so that the staining of collagen fibers can be done by Masson Staining. Therefore, after Masson staining, myofibrils appear red and collagen fibers appear green (light green) or blue (aniline blue), which is mainly used to distinguish collagen fibers from myofibrils.

Masson three-color staining features: ① stable staining; ② short differentiation time; ③ clear and bright color; ④ wide range of application, suitable for tissue staining of paraffin sections, frozen sections, etc.; ⑤ the stained sections are preserved for a long time and are not easy to fade.