The types of grain boundaries that make up the interfacial network within polycrystalline solids influence the properties and performance of the material. The population of grain boundary types is anisotropic, meaning that some of the types are found more frequently than others. The origin of these anisotropic populations was unknown until our recent discovery showed that the energy of a boundary is a key factor in determining which boundaries are shrinking and which are growing: low energy boundaries are growing and therefore have longer lifetimes while high energy boundaries are shrinking and have shorter lifetimes. This leads to anisotropic grain boundary populations that are dominated by low energy boundaries. This discovery, made using experimental techniques developed by the CMU MRSEC, has led to a model for the evolution of grain boundary character distributions that will potentially allow the processing of improved materials.