Toward the middle of the sixteenth century, the prolific Giorgio Vasari, a mediocre painter but a respectable architect (he designed the Uffizi in Florence), began to document the lives of the greatest Italian artists. The idea came to him in Rome, during a conversation with the historian Paolo Giovio. Giovio had begun to write in Latin some "eulogies" of famous artists, but since he knew little about painting, he hesitated about continuing. Vasari immediately undertook the task in his place. He had already amassed a quantity of notes on his illustrious contemporaries and had collected anecdotes, drawn up lists of works, and purchased sketches and drawings, which he kept in bulging portfolios. He extended his research, drew on new sources, and expanded his catalogue; a few years later, in 1550, Torrentino published Vasari's Vite de piu eccellenti archittori, pittori e scultori italiani, containing one hundred twenty biographies. It told of the great adventure of Italian art, from the primitives to the "moderns," and sought to distinguish three styles and three periods: the age of emancipation (of which the foremost representative was Giotto); the age of maturity (attained with Masaccio); and the age of perfection (begun by Leonardo and completed, according to Vasari, by Michelangelo). He was inventing art history.
-Serge Bramly, from the introduction to Leonardo: Discovering the Life of Leonardo da Vinci