The photodegradation of lauric acid at an anatase single crystal surface was visualized using atomic force microscopy (AFM). Photooxidation was performed for lauric acid thin films with thickness about 80-90 nm to simulate more realistic processing conditions rather than using submonolayer films. It was noticed that lauric acid deposited by spin coating technique formed domain structure at the TiO2 surface. The phenomenon of domain surface decrease without change in the film thickness was observed. This suggests that only molecules at the crystal-air-lauric acid contact line and extended therefrom were degraded. (C) 2008 Published by Elsevier B.V.