After having begun his studies in pharmacology at Cremona, the city in which he was probably born a little after 1510, he then transferred to the University of Padua. Here he had as master the famous anatomist Andrea Vesalio (1514-1564), who appointed him his substitute during his periods of absence from Padua. It was probably during the years in which he was teaching at Pisa (1546-1548) that Colombo elaborated his important theory on pulmonary circulation, also called minor circulation. The mechanism, described in those same years in the study Restitutio Christianismi (1553) by Michele Serveto (1511-1553) was however illustrated more fully in Colombo'swork De re anatomica libri XV (1559), which remained a milestone in the history of studies on the circulation of the blood. Moving to Rome in 1548, he taught at the Sapienza University until the year of his death.