With the advent of high energy x-ray sources it is now possible to follow microstructural evolution in three dimensions and as a function of time. The ability to observe and quantify the the evolution processes provides fundamentally new insights into factors controlling the microstructure of materials.  We illustrate this through observation of the high-temperature microstructural evolution of a solid oxide fuel cell Ni-Yttria-stabilized zirconia (Ni-YSZ) anode. Unlike prior studies that compared microstructural differences between different anodes, this three-dimensional measurement directly shows the changes occurring in the same region of an anode, enabling a new understanding of evolutionary processes. High-temperature ageing for 48 h at 1050 °C yielded substantial structural changes in the Ni, YSZ and pore networks, including coalescence of Ni particles, leading to a three-fold decrease in three-phase boundary length. The implications for long-term degradation of fuel cells will be discussed, as well as time resolved x-ray tomography.