Thin films and surface coatings present special challenges in characterization to establish structure-composition-property relationships. Some of the unique challenges will be illustrated and analytical approaches used to solve the problem will be discussed. Examples will include the identification of equilibrium and non-equilibrium phases at interfaces, interfacial segregation, depth profiling using sputtering, angle lapping and angle-resolved data, and kinetics of transformations in thin films and at interfaces. The techniques used will include electron and ion spectroscopies, electron microscopies, and X-ray analysis.