This chapter gives a rapid overview of the history of Roman public and private institutions, from their early beginning in the semi-legendary age of the kings to the later developments of the Imperial age. A turning point has been the passage from the kingdom to the republic and the new foundation of citizenship on family wealth, instead of the exclusiveness of clan and lineages. But still more important has been the approval of the written legislation of the XII Tables giving to all citizens a sufficient knowledge of the Roman legal body of consuetudinary laws. From that moment, Roman citizenship was identified with personal freedom and the rule of law. Following political and military success, between the end of IV and the first half of III century bce Rome was capable of imposing herself as the central power in Italy and the western Mediterranean. From that moment Roman hegemony was exercised on a growing number of cities and local populations, organized in the form of Roman of Latin colonies or as Roman municipia. Only in the last century bce were these different statutes unified with the grant of Roman citizenship to all Italians. In this same period the Roman civil law, which was applied to private litigants by the Roman praetors, had become a very complex and sophisticated system of rules. With the empire the system did not change abruptly, although the Princeps did concentrate in his hands the last power of the judiciary and became the unique source of new legislation. In that way, for the first time, the Roman legal system was founded on rational and coherent schemes, becoming a model, which Antiquity transmitted to the late medieval Europe.