The last decade has seen a tremendous evolution of x-ray imaging and microscopy. This has been driven by the rapid development of third and fourth generation x-ray facilities, as well as new laboratory sources and x-ray optics capable of producing beams routinely below 50 nm in size. The high penetrating power, extreme sensitivity of x-rays to strain and defects and the tunability of these new sources to access x-ray fluorescence of much of the periodic table has enabled in situ or operando studies of nano-scale properties materials. It is worth also emphasizing that small x-ray beams may also be used to induce an electrical current or light emission in the nano-object enabling enhanced scanning probe and photo excitation studies.Beyond a discussion of the methods which have been developed, and are still an object of active research (coherent diffraction imaging in forward or Bragg or full field imaging conditions, nano x-ray fluorescence imaging, micro-Laue diffraction …), this symposium aims to review the materials science issues that these new tools can help solving. The range of materials science topics and related applications is indeed very large: electronic and optoelectronic devices (including flexible devices), transport properties, photovoltaic applications, catalysis, energy harvesting and storage, and even structural materials.