Last week I spent some time in Orvieto, a city a couple of miles north of Rome. In the time of St. Thomas Aquinas' residence there, it was part of the papal state, and St. Thomas had access to the Holy Father's libraries and was often asked to give him counsel, walking to the papal palace along streets like this one.
One of the confusions of the heresy had to do with the Eucharist and whether the Blessed Sacrament was really the Body and Blood of Christ. So as often happens, the Lord provided a Eucharistic miracle, in which blood appeared on the corporal in which a host was being carried. Popular piety once again united around the Blessed Sacrament, and to this day, Corpus Christi is celebrated with great solemnity and processions through the streets of the city.
The miracle led to the promulgation of the Feast of Corpus Christi, and throughout the churches of Orvieto there are a number of depictions of St. Thomas' offering of his written office of the feast to the Holy Father, as well as of the Lord's speaking to St. Thomas from the crucifix, assuring him that he had spoken well of the Blessed Sacrament.