Transubstantiation is a belief in the Catholic Church that during the Eucharist, the bread and wine used in the ceremony become the actual body and blood of Jesus Christ. This change is not visible; instead, it is understood to occur at a spiritual level. The substances of bread and wine transform, while their appearances remain the same. This doctrine emphasizes the importance of the sacrament as a way for believers to connect with Christ. By partaking in the Eucharist, Catholics believe they are receiving divine grace and participating in a sacred mystery that has been central to their faith for centuries.