Mark Littler is Professor of Criminology at the University of Greenwich, UK. His research focuses on online environments, processes of radicalization, and policy responses to extremism. He is co-chair of the European Society of Criminology Working Group on Radicalization, Extremism, and Terrorism (WG-EXTREME), Associate Editor of Behavioral Sciences of Terrorism and Political Aggression and Perspectives on Terrorism, and Series Editor for Routledge Studies in Digital Extremism. Elanie Rodermond is Associate Professor in Criminology at the Criminal Law and Criminology department of the Vrije Universiteit Amsterdam, Netherlands and researcher at the Netherlands Institute for the Study of Crime and Law Enforcement (NSCR). Her research focuses on the life course, criminal career and reentry experiences of offenders, most notably extremist and terrorist offenders. Elanie is coordinator of the Criminology Master programme, co-chair of the European Society of Criminology Working Group on Radicalization, Extremism, and Terrorism (WG-EXTREME, associate editor of Behavioral Sciences of Terrorism and Political Aggression and editor of the Dutch journal Sancties [Sanctions].