Devotion to the Sacred Heart of Jesus came into the Catholic faith through a Catholic sister known as Saint Margaret Mary Alacoque.

(1647-1690). At the age of 24,  Margaret Mary entered the Visitation convent at Paray-le-Monial in France. She began to have visions of Our Lord and on December 27, 1673, on the Feast of St. John, she began to have visions that lasted for eighteen months. Jesus told her that she was to become his instrument in spreading devotion to his Sacred Heart. While kneeling before the Blessed Sacrament, Our Lord appeared to her and invited her to "rest a long time on His Divine Breast". Jesus revealed to her the marvels of the love that His Sacred Heart had for mankind.

Jesus said to her: "MY DIVINE HEART IS SO FULL OF LOVE FOR MEN AND FOR YOU IN PARTICULAR THAT, NO LONGER ABLE TO CONTAIN WITHIN ITSELF THE FLAMES OF ITS BURNING CHARITY, IT MUST SPREAD THESE FLAMES BY MEANS OF YOU, AND IT MUST MANIFEST ITSELF TO MEN IN ORDER TO ENRICH THEM WITH ITS PRECIOUS TREASURES. I HAVE CHOSEN YOU TO ACHIEVE THIS GRAND CRUSADE OF LOVE."

    Saint Margaret Mary had frequent visions of the  Sacred Heart of Jesus.  According to Saint Margaret Mary, His Divine Heart was "more radiant than the sun and as transparent as crystal," with its adorable wound visible, and as a "furnace" of burning flames.

    In June, 1675: during the feast of Corpus Christi, while praying before Our Lord in the Most Blessed Sacrament of the Monstrance. Our Lord revealed His Heart to her and said: "HERE IS THE HEART THAT HAS SO LOVED MEN AS TO SPARE NOTHING FOR THEM, EXHAUSTING AND CONSUMING ITSELF IN ORDER TO PROVE ITS LOVE FOR THEM; AND IN RETURN I RECEIVE, FROM MOST OF THEM, ONLY INGRATITUDE."