St. Anne with Mary, the daughter immaculately conceived in her womb, with the child Jesus. c. 1510; oil on wood; Musée du Louvre, Paris: click on image for larger version, detail
Here is the text of the document by which Pope Pius IX defined and declared the dogma of the Immaculate Conception in 1854.
This poem says it all: briefly, but beautifully...
The Immaculate Conception
A dewdrop of the darkness born,
Wherein no shadow lies;
The blossom of a barren thorn,
Whereof no petal dies;
A rainbow beauty passion-free,
Wherewith was veiled Divinity.
- John Bannister Tabb