A tough challenge in nanomaterials chemistry is the determination of the structure of multicomponent nanosystems. Dye–zeolite L composites are building blocks of hierarchically organized multifunctional materials for technological applications. Supramolecular organization inside zeolite L nanochannels, which governs electronic properties, is barely understood. This is especially true for confined close-packed dye molecules, a regime not investigated in applications yet and that might have great potential for future development in this field. Here we realize for the first time composites of zeolite L with maximally packed fluorenone molecules and elucidate their structure by integrated multitechnique analyses. By IR spectroscopy, thermogravimetric analysis, and X-ray diffraction, we establish the maximum degree of dye loading obtained (1.5 molecules per unit cell), and by modeling we reveal that at these conditions fluorenone molecules form quasi 1-D supramolecular nanoladders running along the zeolite cha...