[quicktime]https://www.ub.edu/elle/wp-content/uploads/grainboundarysweeping.mov[/quicktime]
Development of grain boundary migration growth bands. Development of remnant unswept cores during grain growth, after 0, 500, 1000 and 1500 time steps. At each stage of the evolution, areas never swept by grain boundaries are left green, and areas swept at least once by a migrating boundary are coloured white. Grain boundaries are shown as black lines. At every stage of the evolution the vast majority of grains possess a core of unswept material. Some of these cores at each stage are in contact with the grain boundary network, whereas others are completely isolated from it. Mark Jessell