Graph coarsening for multilevel organization. The coarsening process is visualized in a sub-network of Ito-Core (8 nodes, 10 edges). The arrows and highlighting indicate those nodes that are combined into a new metanode (MN). At the first level of the coarsening (1), nodes N2 and N3; nodes N4 and N8; and nodes N6 and N7 are merged into metanodes MN1, MN3, and MN2 (2). At the next level (3), node N1 and metanode MN1 are merged into a new metanode MN3; and node N5 and metanode MN2 are merged into metanode MN5. Finally, after merging metanodes MN5 and MN3 into metanode MN6 (4), there are only two nodes left and the coarsening process is finished (5).