The XXIII International Materials Research Congress was held on August 17–21, 2014, in Cancún, Mexico. It was organized by the Sociedad Mexicana de Materiales (SMM). About 1,500 specialized scientists from more than 40 countries participated in the 30 different symposia, workshops, plenary lectures and tutorial courses. This special issue covers several aspects of the structural and chemical characterization of materials in the following areas: metals, alloys, steels, composites, polymeric compounds, welding, nanomaterials, and surface coatings, among others. They are amorphous, crystalline, powders, coatings, fibers, thin films, and so forth, which were prepared with different techniques. The structural characterization techniques include: scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, optical microscopy (OM), Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA), differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), thermo luminescence (TL), laser emission, amongst others. Theoretical models from these properties are also included.