Open-pored mesoscopic 2D titania layers (see Figure) were fabricated by using a nanoparticle layer as a template. Monodisperse polymer particles approximately 60 nm in diameter were spontaneously formed by dissolving polystyrene-b-poly(N-methyl-2-vinyl-pyridinium iodide) in toluene. These particles self-assembled at the air-water interface to form well-ordered monolayers. which were then used as templates in a sol-gel reaction to form porous 2D titania layers with a pore size of similar to 55 nm.