The solid-solid chemical reactions of phenols or ketones, such as beta-naphthol (1) or anthron (2), with FeCl3. 6H(2)O by ultraviolet irradiation give coupling dimeric products. The mechanisms are studied using atomic force microscopy (AFM) and known crystal packing data. AFM reveals that the crystal face (100) of 2 or (001) of 1 exhibits stumpy protrusions all over the surface from the contact edge of the crystals, respectively, whereas the long side face (010) of 2 gives volcanoes. All of those are guided by the crystal structure. Molecular interpretations of the AFM features are given.