Organic microdots of fluorescent bis(NN-di-p-tolylamino-p-styryl)benzene molecules were self-organized by vapor deposition onto the KCl (001) surface kept at 180 degreesC. In situ optical microscopy revealed that the microdots preferably nucleated themselves along the KCl [100] step so that they were aligned partly in a linear manner. As the deposition was continued, the number of nuclei reached the saturation point and their diameters increased from a few submicrometers to several micrometers. Finally, the adjacent microdots coalesced resulting in a diameter larger than 10 mum. Such microdot growth was attributed to molecular migration on the substrate surface with a long diffusion length based on the molecular bearing effect of the peripheral bulky group. The as-deposited microdots exhibited a bluish-green fluorescence, which was considerably quenched under UV excitation in air due to photooxidation of the pi -conjugating backbone. When the microdots were covered with a MgF2 layer, this fluorescence quenching was thoroughly prevented.