As stated by Richard Vinci and Oliver Kraft in the announcement of 2008 Gordon Research Conference on Thin Film and Small-Scale Mechanical Behavior, there is a compelling need to understand the critical roles of different deformation mechanisms in structures with small characteristic dimensions, like nanocrystals and thin films. We have recently studied deformation behaviors in nanostructured materials and thin films with deformation mechanisms including grain-boundary diffusion, grain-boundary sliding, and grain-interior plasticity. Some interesting mechanical phenomena associated with heterogeneous grain-boundary properties are found and summarized here.