This work involved the study of Cold Lake asphaltenes' behavior in toluene and o-dichlorobenzene. The changes in asphaltene microenvironments with the increase in asphaltene concentration were observed using fluorescence solvatochromism. The reporter molecule chosen was the environmentally sensitive fluorophore PRODAN. This procedure represents a novel and sensitive method to study asphaltene solutions, and might bring additional information to the existent database of asphaltene properties.A pre-aggregation model was developed to explain the experimental observations, and a definition for the critical aggregation concentration was proposed. The model is valid for low asphaltene concentrations and is supported by direct measurements of refractive indices for asphaltene solutions. Atomic force microscopy was used to image asphaltene entities. The size distribution indicated that asphaltene particles do not change significantly with the increase in concentration. The appearance of larger aggregates in solutions with concentrations above CAC might support the validity of the model.