[5] Catherine Labouré stated that on 18 July 1830, the eve of the feast of Saint Vincent de Paul, she woke up after hearing the voice of a child calling her to the chapel, where she heard the Virgin Mary say to her, "God wishes to charge you with a mission.

Around the margin of the frame appeared the words Ô Marie, conçue sans péché, priez pour nous qui avons recours à vous ("O Mary, conceived without sin, pray for us who have recourse to thee").

Catherine then heard the Virgin Mary ask her to take these images to her confessor, telling him that they should be put on medallions, and saying "All who wear them will receive great graces".

[9][10] The chapel in which Catherine experienced her visions is located at the mother house of the Daughters of Charity of Saint Vincent de Paul in Rue du Bac, Paris.

[17] The elements of the design encapsulate major Marian teachings that have been declared doctrine by the Catholic Church.