Appointed cardinal at just 21 through the influence of his uncle, Pope Pius IV, Charles Borromeo seemed destined for a brilliant ecclesiastical career. But a profound spiritual transformation made him one of the great reformers of the Catholic Church. A friend of St. Philip Neri and a key figure in the Council of Trent, he left a lasting mark on the history of Catholicism. In Rome, a basilica still preserves the relic of his heart.