Over the past decade, analysts have proposed several frameworks to explain the process of radicalization into violent extremism (RVE). These frameworks are based primarily on rational, conceptual models which are neither guided by theory nor derived from systematic research. This article reviews recent (post-9/11) conceptual models of the radicalization process and recent (post-9/11) empirical studies of RVE. It emphasizes the importance of distinguishing between ideological radicalization and terrorism involvement, though both issues deserve further empirical inquiry. Finally, it summarizes some recent RVE-related research efforts, identifies seven things that social science researchers and operational personnel still need to know about violent radicalization, and offers a set of starting assumptions to move forward with a research agenda that might help to thwart tomorrow's terrorists.