First Ask What is a Complex System

A complex system must be understood not just in terms of the set of components out of which it is constructed, but the topology of the interconnections and interactions among those components. Any measure of complexity must likewise respect both the structure and dynamics of a complex system. 

fluids, crystals, and lasers are all examples of complex systems that are familiar to ns from physics. Chemical reactions, in which a large number of molecules conspire to produce new molecules, are also good examples. From biology, we have DNA molecules built up from amino acids, cells built from molecules, and organisms built from colls. 

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