Using three-dimensional electron backscatter diffraction, we have studied the microstructures of a variety of metals and ceramics. From these data, we have measured the grain boundary character distribution, the relative grain boundary energies, and the grain boundary curvature distribution. For the cases of Y-doped Al2O3 and SrTiO3, we have also analyzed grain boundary thermal grooves at different temperatures to determine how the relative grain boundary energy changes with temperature. We have found that there are abrupt changes in the grain boundary energy and the distributions of grain boundary planes that are consistent with grain boundary complexion transitions. For example, in SrTiO3, in the temperature range where there is a well-known decrease in the grain growth rate constant, there is also a decrease in the relative grain boundary energy and an increase in the fraction of grain boundaries with the (100) orientation. The distribution of grain boundary energies and curvatures indicates that grain boundaries with these orientations have the lowest relative energies and also the lowest curvatures, suggesting a reduction in the driving force for grain boundary motion. The impact of these changes on the grain growth rate constant will be discussed.