Nuclear reactors are extreme environments which have many environmental effects which occur simultaneously including irradiation, corrosion, aging, and creep. This can cause unique oxidation of materials, enhanced precipitation, and kinetically driven (rather than thermodynamically driven) segregation. Many of these phenomena can be detected using other methods, but techniques even as high magnification as transmission electron microscopy fail to deliver both high resolution atomistic scale chemical information, 3-D chemical mapping, and suffer from limited chemical resolution. Atom probe tomography can provide new insights into fundamental mechanisms and microstructures in nuclear materials which have significant impacts on nuclear materials performance. In this webinar we will discuss some of the specific topics in nuclear materials development and how atom probe can be used in combination with other techniques to understand materials behavior in extreme environments.