Today we recognize that Saint Charles is precisely one of those saints to whom the word was given "to make the Gospel known," of which he was "ambassador." He carried out this mission in an heroic way with the total dedication of his might: in an early period, in the Council of Trent period, in works in which he actively participated from Rome, bearing the weight of a nurtured correspondence, collaborating to bring to success the conciliar fathers collegial fatigue ... Then, the cardinal, as archbishop of Milan, successor of St. Ambrose, becomes the tireless director of the resolutions of the Council, translating them into practice through various diocesan synods.

The Church owes him a radical renewal of the clergy, the creation of the seminars, whose origin dates back precisely to the Council of Trent, contributed to that renewal. He did many other works, among which the establishment of the brotherhoods, of the pious associations, of the lay-Oblates (who already foreshadowed the Catholic Action), schools, hospitals for the poor, and finally the foundation of the University of Brera in 1572.

- His life could be synthesized in three magnificent expressions: he was a holy Shepherd, an enlightened teacher and a prudent and sagacious legislator.