This work presents a novel and sensitive procedure to study the behavior of asphaltene solutions in toluene and o-dichlorobenzene. Fluorescence solvatochromism was used to observe changes in asphaltene microenvironments with the increase in asphaltene concentration. The environmentally sensitive molecular probe PRODAN (6-propionyl-2-(N,N-dimethylamino)naphthalene) was selected as the reporter molecule to provide clues as to the polarizability in the vicinity of asphaltene molecules. PRODAN displays substantial polarizability-induced shifting of its maximum fluorescence intensity, a feature that was exploited to characterize the various microenvironments found in asphaltene systems. A preaggregation model was developed to explain the experimental solvatochromic observations, and a definition for the critical aggregation concentration was proposed.