The Solemnity of the Annunciation is significantly important in our reflection on Christ's Incarnation as Man. It looks forward nine months to our observance of Christ's Nativity. Our Lord took flesh in the womb of Mary, full of grace. The Blessed Virgin Mary guarantees Christ's humanity and, because He shared in our humanity, we can, by grace, come to share His divinity. This is why the Blessed Virgin, Theotokos, was central to the christological controversies of early Christianity.
From the Collect of the Mass for the Annunciation (New Translation):
O God, who willed that your Word should take on the reality of human flesh in the womb of the Virgin Mary, grant, we pray, that we, who confess our Redeemer to be God and man, may merit to become partakers even in his divine nature.How cool is this? God is good!