About the cover
Control theory can be used to steer engineered and natural systems towards a desired state, but a framework to control complex self-organized systems is lacking. Can such networks be controlled? Albert-László Barabási and colleagues tackle this question and arrive at precise mathematical answers that amount to 'yes, up to a point'. They develop analytical tools to study the controllability of an arbitrary complex directed network using both model and real systems, ranging from regulatory, neural and metabolic pathways in living organisms to food webs, cell-phone movements and social interactions. They identify the minimum set of driver nodes whose time-dependent control can guide the system's entire dynamics. Surprisingly, these are not usually located at the network hubs. On the cover, part of the cactus structure, a subset of nodes that have a key role in the control of real networks, with nodes in blue and drivers in red, visualized by Mauro Martino ( go.nature.com/wd9Ek2).
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