
Cover image: Communities in the giant component of the worldwide air transportation network. Each spot represents a city, and each color corresponds to a community of easily connected cities. Analysis reveals that the most important hubs, which serve as connectors between communities, are not necessarily the busiest ones or the most centrally located. See the article by Guimerà et al. on pages 7794–7799. Image courtesy of Luis A. N. Amaral and Roger Guimerà.