Anodization of a polycrystalline TiO2 electrode in a sulfuric acid solution under UV light irradiation causes photoelectrochemical dissolution (photoetching) with current efficiencies of several percent and hence leads to a unique microfabrication of its surface. Control of the electrode potential made it possible to dissolve selectively the grain boundary or the grain bulk of the electrodes. Upon photoetching the electrode under weak anodic polarization, namely, at a potential close to the photocurrent onset, a 'skeleton' structured TiO2 surface consisting of grain boundaries evolves as a result of a selective dissolution of the grain bulk. The micro-structural study of the grain boundary was carried out by transmission electron microscopy (TEM). The remaining grain boundary has a sandwich structure that consists of two thin platelets of crystalline phases of TiO2 attached each other, having different crystal orientations.