The first volume of The South in the history of Italy. “Two Italies” in the Middle Ages? North and South differentiation and complementarity (VII-XII centuries) much differs from school manuals and from university manuals of medieval history. The research work of this essay is based on a close link between interdependence and differentiation between north and south from the XII-XIII century. The Author, retracing the historical evolution of Italy of the time and understanding the specific peculiarities of economic structures, social and political emphasizes the elements of Unity and the elements of Differentiation of the South in that particular historical period. The South Historical Events, filtered through the life of the territorial communities and of the Norman-Swabian dominion are connected to the history of the Italian “nation” and to the particular situation of South Italy within the Mediterranean bringing “new light” on that distant age. “Two Italies”, therefore, even in the Middle Ages? This is the question this essay tries to answer.