Vasari does not just tell the stories of the artists' lives. He also describes their artworks in great detail. It is because of Vasari that art historians know of many important artworks that have been lost. It is because of Vasari that we know that the Mona Lisa once had eyebrows. Vasari writes about the artworks as a history. He believed that the Gothic art of the Middle Ages was not as good as the art of Florence in the 15th century (1400s) and that Michelangelo, who painted in the early 16th century (1500s) was the greatest artist since the days of Ancient Greece. He believed that the change towards the great art of the Renaissance began with Giotto around 1300. Vasari puts all these ideas into his book and shows how one artist learnt from each other, and how the changes in art came about. "Vasari's Lives" is the first art history book that was ever written.