St. Catherine Laboure, A sister in France in 1830, was given the grace to have Mary visit with her 3 times.
The second time, St. Catherine saw her standing on a globe with rays of light streaming from her hands. Around Mary were the words:
"O Mary conceived without sin, pray for us who have recourse to Thee."
Mary told St. Catherine to have a medal made that looked exactly like that.
St. Catherine did what Mary told her. The medals were called the Medal of the Immaculate Conception. As soon as people started wearing the medals, miracles were happening.
People started calling them the Miraculous Medal.