In this study, aggregation-induced emission (AIE) properties of trans-stilbene, which can be considered as a smaller chemical structure of tetraphenylethylene (TPE) were investigated in different organic-water systems. In this regard, the UV light absorption and fluorescence spectra of trans-stilbene in different compositions of THF/water and dioxane/water systems were measured, and the effects of pH on the spectra were evaluated. It was found that in THF solution, trans-stilbene is non-emissive but it becomes emissive at aggregated states due to restriction of intramolecular rotation with respect to the C-C bond, similar to TPE. The emission intensity of the trans-stilbene in organic-water systems was found to be affected by medium pH through the formation of aggregates. The photoluminescence study indicated that the fluorescence spectra consist of two emission bands assigned to single and two-photon processes. This finding offers an interpretation that AIE may involve two-photon process, rather than just simple fluorescence intensity changes. The present study highlighted a new horizon towards the AIE phenomena.