He studied at the State University of Milan. In 1966 he wrote the book Il gotico internazionale in Italia (The International Gothic in Italy) for Roberto Longhi within the series he directed La pittura italiana. He taught Medieval Art History at the University of Verona and held the chair of Medieval Art History at the State University of Milan for twelve years from 1986.
He mainly devoted himself to the study of 14th- and 15th-century painting, with particular attention to the artistic circulation between Italy and the transalpine countries[2]. Moreover, he investigated the problem of the grafting of Tuscan culture into 14th-century Lombardy[3]. He also dealt with the role and importance of the so-called minor arts during the Middle Ages [4]. In particular, he devoted himself to the study of miniature painting in the Visconti era, a field in which he contributed to the understanding of the figure of Michelino da Besozzo, among others. Finally, he also worked on miniature painting and goldsmithing from the Ottonian period.