Far-field fluorescence of Langmuir-Blodgett (LB) films of the hemicyanine dye, 4-(4-(dihexadecylamino)-styryl)-N-methylpyridinium iodide, I, is spectrally heterogeneous, displaying bands assigned to monomer and various aggregated species in both excitation and emission. LB films of I visualized by epifluorescence microscopy were also observed to be spatially heterogeneous. Under the preparation conditions used here the morphology consists of coexisting liquid expanded (LE) and liquid condensed (LC) phases. LC domains display distinct spatial structure. They are ca. 5-20 mum in lateral size, display a multilobed shape, and are surrounded by LE phase. The characteristic aggregation behavior of these stilbazolium-based hemicyanines allowed their electronic spectra to be used to provide the contrast in fluorescence microscopy of LB films of I. Emission images thus reveal the aggregation-induced electronic structure of the molecules composing the domains. The degree of internal structure of the LC domains was observed to vary with excitation wavelength with the richest internal structure being observed with UV excitation of the fully developed W-aggregate. Correlation of film and solution fluorescence spectra suggest that the LC domains are composed of dimers, trimers, and larger n-mers up to the fully extended aggregate, while the LE phase is predominantly populated by monomers with some fully extended aggregates.