One problem with water-based film-forming systems is the high heat of evaporation, yielding long drying times. Short drying times are commonly important, and solvents with high vapour pressures must be used. This fluorescence microscopy method has successfully been used for studies of low and high volume latex fractions, even for particles with a diameter as small as 100 nm. It is possible to perform statistical analyses from single particles traces, yielding information on interactions with other compounds, as well as changes in the environment of the particle. For fast-drying systems, film formation often occurs under non-equilibrium conditions. The microstructure, frequently due to uncompleted phase separation, is decisive for the film properties. Such microstructures have been found in polymer thin films for optoelectronic devices. Of special interest is the recognition of arrested states and so-called Levy walk diffusion at elevated concentrations, the concentration gradient being a consequence of the drying process