Chapter 7 describes the different types of jihadi cells, highlighting their differences as well as some similarities between them. Each cell has a life of its own, and the essence of each is determined by group dynamics, the origins of its leaders, the interactions between its members, and their cultural and economic homogeneity or heterogeneity. Each of these factors plays a significant role in the radicalization and in the effectiveness of the group to implement its goals. In general, cells are loosely structured, and it is very rare to find “egalitarian cells” or “leaderless” groups of friends or buddies, contrary to the claims of some researchers. Sometimes, they have more than one leader, a division of tasks occurring between them (for instance, the ideological and the military). Jihadi actors choose to belong to a group for many reasons: friendship, spatial proximity (they live in the same neighborhood), attendance at the same university, high school, sports association, or mosque, and so on These facets have been frequently studied, some researchers focusing on the horizontal relationships (a group of friends without formal hierarchy) or vertical ones (the presence of a leader and his lieutenants), their actual link with a larger network (al-Qaeda, IS) or imaginary (laying claim or making allegiance without any effective ties), the degree of their dependence on the web, or the greater or lesser scope of the group (from a solo jihadi to large groups of more than ten or fifteen people).