Methods and apparatus for screening diverse arrays of materials are provided. In particular, the present invention provides techniques for interrogating organic materials, inorganic materials, or polymers on predefined regions of a substrate, using optical probe molecules to measure properties of these materials. This invention involves the use of environment-sensitive probes, such as dye probes, to enable parallel, rapid and efficient characterization of important material properties, including glass-transition temperatures, polarity, hydrogen bonding and other intermolecular interactions. These methods can be applied to crystalline or amorphous materials, polymeric or small-molecule materials, pure materials or mixtures, and to materials in bulk, particles, thin films, dispersions, emulsions, and solutions.