Here we see Jesus who has just celebrated the Passover with his disciples. Two ingredients of the Passover meal are of course unleavened bread and wine. Jesus takes these gifts of creation, offers them to the Father (as he is about to offer his life on the cross) and then gives us them to eat and drink. He tells us, 'This is my body' and 'This is my blood.'
How wonderful to know that whenever we celebrate Mass today, we receive the body and blood of Jesus. What a priceless gift. Small wonder the last words at Mass are 'Thanks be to God!'