Figure 1.

Complex networks. (A–C) Some real systems can be abstractly represented by networks. The components of the system are replaced by nodes and their channels of interaction by links. Networks are mathematically encoded into adjacency matrices for their statistical analysis. (D) The nodes of a network often form densely interconnected modules, which can group together to form larger modules and hierarchies. (E) Given a network with modular organization its nodes can take different positions. These can be characterized by two parameters: (i) the global importance of the node or hubness, and (ii) the dispersion of the links of the node throughout the modules, referred as node's participation.