Morphology of 6-methyl merocyanine J-aggregates self-assembled in polyvinyl alcohol (PVA) films by a spin-coating method has been investigated by means of scanning near-field optical microscope and confocal laser scanning microscope. Photoluminescence image measurements show that J-aggregates form different domain structures with a grain-shape and a fiber-shape depending on the concentrations of merocyanine and arachidic acid in the PVA film. From the polarization-dependent measurements, we have found that the 6-methyl merocyanine molecules construct a hierarchical structure of J-aggregates in which a J-aggregate domain is composed of coherent aggregates with the same transition dipole orientation. (C) 2003 Elsevier B.V. All rights reserved.