Metallic nuclear fuels have been studied for decades in various types of reactors, including fast reactors, as well as research and test reactors. Recent improvements in the sectioning and specimen preparation of irradiated fuels and materials have allowed for the small-scale testing of highly irradiated systems. These miniaturized specimens possess a lower dose rate and fewer radionuclides, which enables the possibility of characterization at numerous facilities. Moreover, these improvements are coupled with advanced characterization techniques that allow researchers to gain access to length scales that were previously unattainable. This talk will focus on advanced synchrotron characterization techniques that enable microstructural characterization that spans from two to three dimensions. Radiation effects on atomistic ordering, phases, grains, microstrain, pore formation, and swelling will be discussed. Examples will be provided for both low and high fluence irradiated metallic fuels, including uranium molybdenum and uranium zirconium alloys.