This chapter reviews the literature on co-offending networks and co-participation in crime. It describes the value of the approach by analysing several real-world covert networks. Research on social networks and crime has argued that individuals keep their relationships secret to limit their overexposure and protect their network from law enforcement. The bulk of criminological research that investigates the dynamics of cohesion in covert networks is generally focusing on co-offending networks, and it has mainly focused on street gangs and juvenile groups. The advantage of comparing similar networks is that it focuses on the unique factor responsible for generating different outcomes in the networks. Research on criminal networks remains explorative and descriptive to a large extent. Criminological theories explain changes in co-offending partnerships starting from delinquent roles and criminal careers. The bi-clique analysis not only reveals which individuals have been co-offending the most, but it also identifies relative to which events the partnerships were created and for how long they lasted.