Small Angle Neutron Scattering (SANS) gives evidence of colloidal structures or clusters in solutions of vanillin in aqueous alcohol. Interpretation of the data gives the same result as the Photon Correlation Spectroscopy technique: stable or metastable fractal clusters. The size of these clusters increases as a function of the parameters that control supersaturation, but is stable with respect to time. These structures, called metastable clusters, are closely related to the observed liquid-liquid phase separation at high solute concentration. Another type of clusters is found to co-exist with the metastable clusters at a lower solute concentration. The same type of structures is found in a two-component system of vanillin in 2-methyl-2-butanol. They slowly grow as a function of time, and are called labile clusters. These colloidal structures are assumed to be precrystalline clusters giving rise to nuclei in crystallization.