51 Ambrose, the Bishop of Milan, in a clear statement on the Eucharistic conversion, has this to say: "Let us be assured that this is not what nature formed but what the blessing has consecrated; and there is greater power in the blessing and in nature, since nature itself is changed through the blessing." To confirm the truth of this mystery, he recounts many of the miracles described in the Sacred Scriptures, including Christ's birth of the Virgin Mary, and then he turns his mind to the work of creation, concluding this way: "Surely the word of Christ, who could make something that did not exist out of nothing, can change things that do exist into something they were not before. For it is no less extraordinary to give new natures to things than it is to change nature." (55)
Source: Mysterium Fidei (Vatican.va)