Networks are ubiquitous; they can be found at every turn, from alliance formation to opinions, from rivers to species migration, from proteins to computers and the internet, from trade to disease spreading, from friendship to co-working and innovation. How entities (people, countries, proteins, species, landscapes, etc.) are linked to each other often affects how processes unfold (i.e. the resilience of food-webs, the spread of information on the internet, the ability to reduce or facilitate contagions and trade, or how opinions and ideas are shared). In other words, structure influences process, and thus the underlying network structure (how things are linked to each other) affects overall system behavior. Network structure thus helps us understand individual components and their collective behavior.