While yet engaged, God sent the Angel Gabriel to Mary at Nazareth. He said, "Hail, full of grace! The Lord is with you. Blessed are you among women. Do not fear, Mary. You are to be a mother, and to bear a Son, and to call Him Jesus. He will be the Son of God, and the King over all His people.
"How will that be?" Mary asked.
The angel answered, "The Holy Spirit will come upon you and by His power the Child to be born of you will be the Son of God.
Mary said, "See, I am the servant-girl of the Lord. May all that you have said be done in me!"
At that moment the Son of God became man under her heart.
Mary My Mother - Chapter 5
Father Lovasik S.V.D.
Catholic Book Publishing, 1978