Communication: Two important microcavity effects-fluorescence intensity enhancement and lifetime shortening-are demonstrated to be exhibited by new microcavities consisting of a pure terbium complex sandwiched between silver mirrors. The advantages of the use of the fluorescent rare-earth complex as the emitting material and the Langmuir-Blodgett technique for the construction of microcavities are discussed. Microcavities acting as optical resonators have potential applications as high-density light sources for optical communications and color displays.