In the Second Eucharistic Prayer at Mass, the priest prays: "We humbly ask you (Father) to make them holy by the power of your Spirit, that they may become the Body and Blood of your Son, our Lord Jesus Christ, at whose command we celebrate these mysteries." This is called the "epiclesis", it is the invocation of the Holy Spirit over the elements of bread and wine. We believe that these elements become the Body and Blood of Jesus by the coming of the Holy Spirit and the words of Jesus. Just as the Son of God became Man in the womb of Mary by the overshadowing of the Holy Spirit, so bread and wine are transubstantiated as the Body and Blood of Jesus, true God and true Man. The words of the invocation is accompanied by the imposition of the hands of the priest over the bread and wine. 

Here is the reflection of Pope St. John Paul II: “In the sacrifice of the Son of Man the Holy Spirit is present and active…. The same Christ Jesus in his own humanity opened himself totally to this action…[which] from suffering enables salvific love to spring forth” (Dominum et Vivificantem. 40).

Be attentive to these words next time you participate in Mass and give thanks to the Father through Jesus in the Spirit for the gift of Eucharist.