Then each box is replaced by a node(renormalization). The  renormalized nodes are connected if there is at least one link between the unrenormalized boxes. This procedure is repeated until the network collapses to one node.
Subsequently, each compartment is transformed into a node (redesignation). The redesigned nodes are linked if there exists a connection between the unaltered compartments. This procedure is iterated until the network diminishes to a single node.