From time immemorial the rich and powerful have wanted to show off their wealth by owning important works of art. The Egyptian and Mesopotamian Imperial houses monopolized artistic production, commissioning enormous works. In the Greco-Roman world the town leaders used art as political propaganda in the same way as the Roman Emperor and at this time patricians and wealthy individuals had already started to collect art on a small scale. During the Middle Ages the Church was the main patron of the arts. During the Renaissance the clients and patrons were no longer restricted to the church sphere. The royal houses wanted to show off their power through magnificent commissions, being imitated by the court of nobles that had grown up around them. Meanwhile the ecclesiastical power did not cease in its mission to create an art that illustrated its teachings. However, it was not until the 18th and 19th centuries that the private collecting boom took place. The bourgeoisie held the economic, political and social power and started on the path to the acquisition of works of art to decorate their houses, offices, banks, companies and so on. Galleries and art dealers appeared who supplied the new clients with modern art. These clients were either millionaires eager to create important collections with which to impress their friends and make their enemies jealous or members of the middle classes who saw art as an investment. As a result private art collections proliferated, which were always a great joy to their owners, whatever their size.