In Exercitatio anatomica de structura et usu renum (1662; “Anatomical Exercise on the Structure and Function of the Kidney”), published when he was a 19-year-old student at the University of Pisa, Bellini showed for the first time that the kidney consists of an immense number of tiny canals. A professor at Pisa for 30 years, Bellini described the taste organs (1665) and stressed the value of urinalysis as an aid to diagnosis (1683). He was a pioneer in the attempt to explain physiological functions through appeal to physical principles. After retiring from the university to Florence (1693 or 1694), he became physician to Duke Cosimo III and Pope Clement XI.