The Mass is where Catholics celebrate the real presence of Jesus through the Eucharist. It has two main parts - the Liturgy of the Word, where scripture is read and God speaks to us, and the Liturgy of the Eucharist, where bread and wine become the body and blood of Jesus through which we are united to him and each other. The Mass began at the Last Supper when Jesus shared bread and wine with his disciples and commanded them to continue celebrating it in memory of him, which Christians have done every Sunday since.