The microstructure and mechanical behavior of polymeric-based materials can be controlled at the micro- and nanometer length scales through blending, copolymerization, and the incorporation of micro- and nanometer particles. To facilitate the study of morphology, deformation mechanisms, and mechanical properties of micro- and nanocomposite materials, a tensile testing machine with an integral commercial atomic force microscope (AFM) was designed and built. This testing machine determines the macroscopic stress–strain behavior of materials under different controlled loading conditions, and simultaneously allows the microscopic structure changes to be observed using the AFM.