What differentiates Catholics from other Christians is our belief in the Eucharist. The Eucharist is the source and summit of the Catholic life. Catholics believe that the Eucharist is the Body, Blood, soul, and divinity of Christ fully present in the form of bread and wine. The sacrifice of the Mass not only recalls, but is the Last Supper. When the priest lifts up the bread and the wine, they become Christ's body and blood, a principle we call transubstantiation. This is why it is important to attend Mass every Sunday, to receive Christ every week.