The surface properties of microheterogeneous systems can be studied by electronic absorption and fluorescence spectroscopies when an aromatic compound is introduced in the colloidal system as a probe molecule. In this chapter, the photophysical characteristics of rhodamine 6G (R6G) adsorbed on several smectite-type clays, laponite (Lap) hectorite (Hect), montmorillonite (Mont) and saponite (Sap), and on sepiolite (Sep) in diluted aqueous suspensions are analyzed. The elucidation of the adsorbed species on different clay surfaces and their evolution with the loading of the dye on the clay and with the ageing of the samples provides information on the dispersion degree, the swelling and the accessibility of the interlamellar space of clays. These colloidal properties depend on the nature of the clay, the particle size and on the concentration of the clay in the suspension.