Recent advances in x-ray and neutron sources, optics, and scattering methods are heralding a new age in the study of the structure and properties of complex materials. By providing unprecedented resolution in real space, reciprocal space, and time, new techniques address materials characterization challenges beyond anything possible before, at length scales ranging from the atomic scale to the mesoscale, and at times as short as femtoseconds. The high degree of coherence of third-generation synchrotron sources permits a new level of precision in the quantitative description and analysis of diffraction and scattering and allows beams with sizes probing individual nanostructures to be produced. As a result, in situx-ray and neutron analysis techniques now provide insight into the structure of nanomaterials and yield a more precise set of metrics describing the nanometer-scale structure of materials. Time resolution and in situ studies allow application of these techniques to materials driven far from equilibrium and to the challenging environment associated with materials processing.