The unequal spatial distribution of crime is an enduring feature of cities. While research suggests that spatial diffusion processes heighten this concentration, the actual mechanisms of diffusion are not well understood as research rarely measures the ways in which people, groups, and behaviors connect neighborhoods. This study published in the American Journal of Sociology considers how a particular behavior, criminal co-offending, creates direct and indirect pathways between neighborhoods. Analyzing administrative records and survey data, the authors find that individual acts of co-offending link together to create a “network of neighborhoods,” facilitating the diffusion of crime over time and across space and, in so doing, create pathways between all Chicago neighborhoods. Statistical analyses demonstrate that these neighborhood networks are (1) stable over time; (2) generated by important structural characteristics, social processes, and endogenous network properties; and (3) a better predictor of the geographic distribution of crime than traditional spatial models.