Van Gieson's trichrome is used for the differentiation between collagen and smooth muscle in tumors and to demonstrate the increase in the amount of collagen in these pathologies.

Van Gieson's trichrome is composed of 3 different dyes: Weigert's hematoxylin for nuclei, picric acid for cytoplasm and fuschine acid for collagen.

When combined solutions of picric acid and acidic fuchsin are used, small picric acid molecules penetrate rapidly into all tissues, but are firmly retained only in red blood cells and muscle. Larger fuchsin molecules displace the picric acid molecules of collagen fibers, which have larger pores, and allow large molecules to enter.

Here are some examples of stains obtained with Van Gieson's trichrome: