We have studied the onset of crystallization from solution using a fluorescent probe molecule that incorporates selectively into precrystalline glucose aggregates that form in supersaturated aqueous glucose solutions. We achieve incorporation of the fluorophore into the aggregates by virtue of the fluorophore pendant glycosyl moiety and compare the rotational diffusion data for this molecule to that for the nonglycosylated, native probe molecule. This experimental approach, in conjunction with semiempirical calculations to understand the electronic response of the fluorescent probe, provides insight into the formation and size of precrystalline glucose aggregates. Our data indicate that the aggregates effectively isolate the fluorophore from the solution over a range of glucose concentrations spanning the saturation point and that the lifetime of these aggregates is on the order of a nanosecond for aggregates that include the glycosylated probe molecule. The subtle but important differences between these results and those we reported previously for carminic acid in aqueous glucose solutions point to the significant role of labile protons in mediating the formation and dynamics of precrystalline glucose aggregates.