Giorgio Vasari's Lives of the Most Excellent Painters, Sculptors and Architects is our most important source of information on Italian art to the mid-sixteenth century. The enlarged second edition ran to more than 1,500 pages in three volumes and featured 163 biographies, many of living artists. Vasari tried to secure authentic portraits for the headpiece to each biography; that of Leonardo was based on Francesco Melzi's portrait of Leonardo (no. 96), which Vasari saw when he visited Villa Melzi.

No. 137