Metal supercomplexes form on compression of a film of the individual complexes mixed with a fatty acid: A suite of techniques-Langmuir film balance, and optical and scanning force microscopy-show the transformation of [Eu(tta)3 (phen)] into a thin film of strongly luminescent tetrameric supercomplexes. When the area per molecule is low, a phase-separated meshwork structure forms. The cartoon shows the surface arrangement, in which the supercomplexes sit on a layer of the single europium complexes and corralled by a fatty acid.