God the Father --> in the Old Testament as the Creator
in the New Testament as the Father (during Jesus' baptism and Transfirguration)
God the Son --> Catholics believe that Isaiah's prophecies refer to Jesus as the son of God, describing a child who will be Mighty God and Prince of Peace
-at the annunciation --> Angel Gabriel tells Mary she has conceived God's son
-at Jesus' baptism --> "This is my son, whom I love"
God the Holy Spirit --> Roman Catholic teaching says the Spirit that surrounds the unformed world