Network science

The study of complex systems whose behavior and responses are determined by exhcanges and interactions between subsystems across a well-defined (possible dynamics) set of pathways,  The central point is that the behavior of a network is determined both by the pathways (structure) and by the exchanges and interactions (dynamics).  Moreover the structure itself may be (and usually is) dynamics.  This is a flexible definition that allows flexible interpretation in the various applications domains.  (Network Science, National Research Council of the National Academies)

Network Science in Three Important Ways 
History of Network Science