This article presents new ex situ techniques, as well as novel applications of conventional methods, to:investigate phase transformations and associated microstructures in polycrystalline thin films. Specifically, we review the results of a dark-held transmission, electronmicroscopy study of the disorder-order transformation thermodynamics and kinetics in CoPt and FePt thin films and, in addition, discuss the applications of differential scanning calorimetry to the interrogation of solid-state reactions in Nb/Al, Ni/Al, and Ti/Al systems. These investigations have naturally prompted the development of methods to analyze and better understand our experimental data. Thus, we also outline a new, automated image processing algorithm for transmission electron micrographs and discuss its implementation to interpret images of thin Al film microstructures. Further, as computer simulation has been employed to highlight important nucleation and growth: parameters, we briefly summarize the results of these investigations.