Criminal organizations are secret societies generally articulated on a hierarchical basis. Members of criminal organizations form groups in order to pursue economic gains. Mafias are criminal organizations whose main characteristic is to seek the monopoly of illegal economic activities. Mafias are a very specialized subset in the set of organized crime groups: they are extra-legal government structures attempting to control the supply of protection. Mafias are groups who aspire to govern markets and territories, offering 'services' to their customers, such as protection against extortion, the elimination of competition, etc. In this class, we will analyze different organizational aspects of mafias, among which: their activities, their rules, norms, and rituals; the organizational levels of mafias; mafia as clan-based form of organization; communication and cooperation among criminals; mafia markets and environments; mafia presence in non-traditional areas. The class will also discuss different orientations and approaches to the study of the Mafia, such as the Mafia as a cultural phenomenon, as hyper centralized organization, etc. Finally, particular attention will be devoted to the phenomena of diffusion to new areas, such as Northern Italy, and the socio-economic factors that makes it possible for mafia organization to take roots in different environments and lines of business.