This is the moment when Angel Gabriel announces to Mary that she will conceive the Christ child. We can see the Angel's announcement literally coming out of his mouth from left to right to Mary. The painting well represents the Sienese style, which differs from the Florence's in the elegance of both line and color. For example, the great detail of Gabriel's wing and the delicacy of the drape flutters as if he has just landed. 

In the middle, we see lilies as symbols of Mary's virginity. In addition to that, Gabriel holds a branch of olive leaves, which is a symbol of Christ bringing the peace, as olive branches traditionally refers back to the story of Noah. We also see in the triangular space above and between Mary and theGabriel, the holy spirit, in the form of a dove, surrounded by angels. The haloed dove emits golden light that moves towards Mary; the light actually emerges from the beak, as if the holy spirit is speaking the divinity to Mary. 

Mary, who is thin and elongated, turns away. The line from the dove to Mary and Gabriel's words forms two sides of a triangle that meets at Mary. However, her cheek and body pull back from being in the center of this attention, showing her slight unwillingness to accept this fact. She has been interrupted, and her finger still holds a place in the Bible, which she has been piously reading at. As Gabriel has arrived, we have a sense of story unfolding here that Mary is about to - but has not yet - say "behold the handmaid of the Lord, be it unto me according to thy word" (Luke 1:38). She hasn't yet accepted her destiny as the mother of God. 

It is really interesting to see how the artist captures this momentary scene and turns it into an absolute and eternal story about the past, the present and the future. The mixture of time and the unity of divinity and human emotion speak to audience as if the painting itself can tell the story of Annunciation. On the top of all these, most essentially, as we see this work, our imagination is inspired, and we think beyond the painting. Thus, the artist's idea raises out of the work itself, and follows our minds to the core of human feeling.