Physicists at the Max Planck Institute of Quantum Optics (MPQ) have engineered the lightest optical mirror imaginable. The novel metamaterial is made of a single structured layer that consists only of a few hundred identical atoms. The atoms are arranged in the two dimensional array of an optical lattice formed by interfering laser beams. The research results are the first experimental observations of their kind in an only recently emerging new field of subwavelength quantum optics with ordered atoms. So far, the mirror is the only one of its kind. The results are today published in Nature.