The local glass transition temperature (T-g) of heterogeneous polymer surfaces has been successfully determined by lateral force microscopy (LFM) on the submicron-nanometer scale. This paper addresses interfacial confinement effects in thin films of blends and emulsions from polystyrene (PS), poly(butylmethacrylate) (PBMA) and poly(methylmethacrylate) (PMMA). The paper addresses the difficulty of thermal rheological experiments with a microscopic scanning technique, and introduces an in-situ calibration method.