Room-temperature solid-state maser. Core of the first ever room-temperature solid-state maser (microwave amplification by stimulated emission of radiation). The core is comprised of a pentacene doped p-terphenyl crystal (pink) surrounded by a monocrystalline sapphire (clear). A maser produces microwaves via atomic resonance (vibrational energy), a phenomenon that occurs when atoms are energised (excited) to a point where they emit radiation. Previous solid-state masers had required cryogenic refrigeration in order to operate. Photographed at the National Physical Laboratory, Teddington, UK.