Network science helps us to better understand the evo-lution of the highly interconnected world in which welive [ 1]. It sheds light on myriad systems — everythingfrom how rumours spread in a social network to how largeecosystems stabilize in spite of competing interactionsbetween species. A key feature shared by such systems isthat they are characterized by a complex set of interac-tions that govern their emergent dynamics [ 2 –4]. In therecent years, the architecture of social networks, ecosys-tems and the human brain have all been modelled asgraphs, with collections of nodes describing the units ofthe systems — humans, animals or neurons — and edgesencoding their pairwise interactions