'Photonic graphene' structures-submicron two-dimensional dielectric structures with a honeycomb lattice- are fabricated by laser lithography. The transition from the regime of light scattering by a metasurface to that of Laue diffraction at a two-dimensional photonic structure in the optical range is studied experimentally and theoretically. The optical diffraction patterns make it possible to determine the number of unit cells in a finite microstructured sample with the naked eye.