The eventful history of the conclave-election (indoors) of the Supreme Pontiff is presented as a mirror of the changing conceptions of the Catholic Church, the papacy and its relationship to political power, and more generally, of the mentality that characterizes different times in the West. Reading this study, particularly well documented, provides an overview of the essence and evolution of the conclave as a fragment-and paradigm-Catholicism from its beginnings to the present day. Alberto Melloni, professor of history at the University Modena / Reggio Emilia and Director of the Institute "Fondazione per le Scienze religiose Giovanni XXIII" in Bologna, offers a fascinating journey through time. In brief but successful features, summarizes the early appointment of the Pope in the first millennium. The author also addresses the crucial changes that causes the eleventh century and to prepare the celebration of the first conclave in 1241 and its subsequent institutionalization and regulation in 1274. Then the crisis and provides new start experiencing the conclave in the late fourteenth century and the transformations that characterize its development until the late nineteenth century. This tour serves as a backdrop for the central part of the work: the history of twentieth-century conclave. After a display of the innovations introduced by Pius X, Pius XI, John XXIII and Paul VI, Melloni extends the provisions of detail about John Paul II, the current legislation to the present. The author enriches his exposure through numerous references to events that have marked this turbulent century, integrating its analysis of the conclave in a broader context. Following in the footsteps of Melloni through his revealing study, the reader will notice the amazing resilience and continuous adaptation to the needs of the moment that the conclave has maintained over time and that have allowed their survival as an institution even in times of crisis. What challenges the new millennium will pose to the Catholic Church and the conclave? Given this fundamental issue, scholarly research take on a peremptory Melloni for theologians today / I, students of theology and religious communities, but also to a public interested in Western history.