This book identifies the three major determinants of radicalization that progresses into violent extremism, the three Ns of radicalization. The first determinant is the need: Individuals’ universal desire for personal significance. The second determinant is the narrative. Because significance is conferred by members of one’s group, the group’s narrative guides members in their quest for significance. The third determinant is the network: membership of one’s group who validate the narrative and who dispense rewards (respect and veneration) to members who implement it. The quest for significance is activated in one of three major ways: (a) through a loss of significance occasioned by personal failure or affront to one’s social identity (e.g., ethnicity, religion, race), (b) through a threat of significance loss if one failed to respond to a challenge or to defend one’s group values, and/or (c) through an opportunity for a significance gain (e.g., becoming a hero or a martyr) by selflessly defending one’s group values. In groups that see their values (e.g., religion, sovereignty, culture) under threat from some (real or imagined) actor, the narrative often justifies violence against the detractor and portrays it as a supreme road to significance. Especially where violence is contrary to the norms of the mainstream society, validation of the violence–significance link by the local network is particularly important. The present 3N model of radicalization and the varied empirical evidence that supports it are leveraged to interpret prior theories of radicalization and to address major issues in the domains of deradicalization and recidivism.