On 18 July 1830, Catherine had an experience that was to change the course of her life. During the night, she was awakened by a child who told her that the Blessed Virgin was waiting for her in the chapel. There, Catherine saw the Virgin Mary sitting in an armchair in a bright light. Mary spoke to her gently, encouraging her to remain faithful to her vocation and to continue her service to the sick.

Mary also revealed to Catherine the design of a special medal, which later became the famous Miraculous Medal. The medal was to feature the image of the Virgin Mary, surrounded by the words "O Mary, conceived without sin, pray for us who have recourse to you." Catherine was charged with making the medal known to the world, assuring that those who wore it with faith would receive great graces.

Although Catherine initially encountered difficulties in gaining acceptance for the medal, she persevered in her mission. In 1832, a cholera epidemic struck Paris, and the Sisters of Charity, including Catherine, were among the first to care for the sick. It was at this time that the medal began to be more widely distributed, and miracles and inexplicable cures were associated with those who wore it.

Catherine remained humble despite the growing fame of the Miraculous Medal. She continued her discreet work in the service of others and never sought attention for herself. She spent the last years of her life in prayer and contemplation, far from the glare of the world.

In 1947, Catherine Labouré was canonised by Pope Pius XII. Her example of humble dedication and trust in the divine will continues to inspire many faithful around the world. The Miraculous Medal remains a symbol of protection and faith for many Catholics, recalling the extraordinary life of this humble nun who responded to the Virgin Mary's call with unshakeable faith.