Explaining the Eucharist: What is transubstantiation?

Many well-intentioned Christians over the years have mistakenly tried to say that the Eucharist is not Christ's real flesh and blood because "the bread and the wine don't change". That's a good point. How do we as Catholic Christians explain our belief in the real presence, if the bread and the wine still look like simple bread and wine?

Think about it, it would be a lot easier if all of the sudden the bread oozed blood or if we used clear glasses and white wine turned into red wine, right?

So, what is "transubstantiation"? Our friend, Webster, defines Transubstantiation as "changing or transforming from one substance into another."

How does the Catholic Church define transubstantiation?
The Catholic Church, at the Council of Trent, summarized transubstantiation "by declaring: "Because Christ our Redeemer said that it was truly his body that he was offering under the species of bread, it has always been the conviction of the Church of God, and this holy Council now declares again, that by the consecration of the bread and wine there takes place a change of the whole substance of the bread into the substance of the body of Christ our Lord and of the whole substance of the wine into the substance of his blood. This change the holy Catholic Church has fittingly and properly called transubstantiation." - CCC 1376

The Eucharistic presence of Christ begins at the moment of the consecration and endures as long as the Eucharistic species subsist. Christ is present whole and entire in each of the species and whole and entire in each of their parts, in such a way that the breaking of the bread does not divide Christ. - CCC 1377

How can YOU explain transubstantiation?
Well, there are two levels that make up an object, the accidents and the substance. The accidents are the appearance, taste, look and feel of an object, but the substance is what it really is.

For instance, if you take a chair it has accidents and substance. Say that you saw the chair in several places and then take those pieces of wood and reconfigure them with nails to make a coffee table. You've changed the accidents of the chair into a table, but the substance of the chair has not been changed, it's still made up of the "wood molecules". Make sense?

So, at Mass...
The accidents of the bread and wine do not change.
The substance of the bread and wine are altered into Christ's body and blood.

In the same way, when you or I receive Christ into us, our exterior appearance may not change, but the grace received by virtue of the Sacrament itself, and the fact that it is truly Christ dwelling within us in the most Incarnational way, shows that while our own accidents don't change, our substance has changed.

It's the same way when we encounter Christ in the Word and internalize it (Lk. 11:28), when we come together as a community and experience His love and fellowship (Mt. 18:20), when we approach the Lord in the Sacraments (Jn. 20:29), like Reconciliation (Jn. 20:22-23), etc. But the grace associated in the uniquely intimate expression of God's grace, through Holy Communion, has a power to transform and "transubstantiate" us like nothing else on Earth.

Further, this comes from the Office for the Catechism, from the United States Conference of Catholic Bishops:
Para. 1413: By the consecration the transubstantiation of the bread and wine into the Body and Blood of Christ is brought about. Under the consecrated species of bread and wine Christ himself, living and glorious, is present in a true, real, and substantial manner: his Body and his Blood, with his soul and his divinity (cf. Council of Trent: DS 1640; 1651).

Source : LIFE TEEN