§1377
Sacraments › … › V. The Sacramental Sacrifice Thanksgiving, Memorial, Presence
The presence of Christ by the power of his word and the Holy Spirit
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.
Source: Catechism of the Catholic Church (Vatican.va)