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.
Then each compartment is replaced by a node (reconfiguration). The reconfigured nodes are connected if there is at least one tie between the unmodified boxes. This process is repeated until the network collapses into a solitary node.