Our biological existence, our ability to communicate, to exchange goods and values, are guaranteed by numerous invisible networks, from the protein and genetic networks in our cells to the world wide web, Internet and financial and trade networks. I will show that the amazingly complex topology of these highly interconnected networks are the result of self-organizing processes governed by simple but generic laws. The ultimate proof of our understanding these complex systems is reflected in our ability to control them. I will therefore explore the controllability of an arbitrary complex network, identifying the set of driver nodes whose time-dependent control can guide the system’s entire dynamics. By applying these tools to real networks, helps us unveil how the network topology determines controllability.