Complex three-dimensional (3D) integrated circuits involving both optical and electronic elements are now easier to make, thanks to a “wafer bonding” technique developed by a European research consortium. Photonics is the science of controlling photons — the particles that make up light. Photonic devices are essential in telephone and computer networks, where they manage the flow of information along optical fibres. Pollution monitors, laser rangefinders, surgical lasers and DVD players are other examples of photonics in action.