She was later transferred to Płock and then to Vilnius, where she met Father Michał Sopoćko, who was to be her confessor and spiritual director, and who supported her devotion to the Divine Mercy.

With this priest's help, Kowalska commissioned an artist to paint the first Divine Mercy image, based on her vision of Jesus.

[10] In 1925, Kowalska worked as a housemaid to save the money she needed, making deposits at the convent throughout the year and was finally accepted, as the Mother Superior had promised.

That year, the first signs of her illness, which was later thought to be tuberculosis, appeared, and she was sent to rest for several months in a nearby farm owned by her congregation.

[11] Kowalska wrote that on the night of Sunday, 22 February 1931, while she was in her cell in Płock, Jesus appeared wearing a white garment with red and pale rays emanating from his heart.

"[17] In November 1932, Kowalska returned to Warsaw to prepare to take her final vows as a nun, by which she would become in perpetuity a sister of Our Lady of Mercy.

[18] Shortly after arriving in Vilnius, Kowalska met the priest Michael Sopoćko, the newly appointed confessor to the nuns.

[18] After some time, Sopoćko insisted on a complete psychiatric evaluation of Kowalska by Helena Maciejewska, a psychiatrist and a physician associated with the convent.

[22] According to Catholic author Urszula Gregorczyk, a superimposition of the face of Jesus in the Image of the Divine Mercy upon that in the already-famous Shroud of Turin shows great similarity.

[23] Kowalska wrote in her diary (Notebook I, Item 414) that on Good Friday, 19 April 1935, Jesus told her that he wanted the Divine Mercy image to be publicly honoured.

[32] In March 1936, Kowalska told her superiors that she was thinking of leaving the congregation to start a new one that was specifically devoted to Divine Mercy, but she was transferred to Walendów, southwest of Warsaw.

In August, Sopoćko asked Kowalska to write the instructions for the Novena of Divine Mercy, which she had reported as a message from Jesus on Good Friday 1937.

[40] It was while assigned to Vilnius that Kowalska was advised by her confessor, Michael Sopoćko, to keep a diary and record her apparitions.

[42] In March 1959, the Holy Office issued a notification, signed by Hugh O'Flaherty as notary, that forbade circulation of "images and writings that promote devotion to Divine Mercy in the forms proposed by Sister Faustina" (emphasis in the original).

[43] It is claimed the negative judgement of the Holy Office was based on misunderstanding due to the latter's use of a faulty French[41][11] or Italian translation of the diary.

However, at the time, the ban was due to "serious theological reservations and what Vatican evaluators felt to be an excessive focus on Kowalska herself.

[41] On 15 April 1978, the Congregation for the Doctrine of the Faith issued a new notification that rescinded the previous one and reversed the ban on circulation of Kowalska's work.

By 1941, the devotion had reached the United States, and millions of copies of Divine Mercy prayer cards had been printed and distributed worldwide.

During that period, Sopoćko used his time to prepare for the establishment of a new religious congregation, based on the Divine Mercy messages reported by Kowalska.

In 1965, with the approval of the Holy Office, Karol Wojtyła, then Archbishop of Kraków and later Pope John Paul II, opened the initial informative process into Kowalska's life and virtues, interviewed witnesses and, in 1967, submitted a number of documents about Kowalska to the Vatican and requested the start of the official process of her beatification.

The Holy See's Press Office biography provided on the occasion of her canonization quotes some of her reputed conversations with Jesus.

[3] The author and priest Benedict Groeschel considers a modest estimate of the following of the Divine Mercy devotion in 2010 to be over 100 million Catholics.

[55] Pope John Paul II said, "The message she brought is the appropriate and incisive answer that God wanted to offer to the questions and expectations of human beings in our time, marked by terrible tragedies.

'"[56] In October 2011, a group of cardinals and bishops sent a petition to Pope Benedict XVI for Kowalska to be made a Doctor of the Church.

[37] Digan had suffered from lymphedema, a disease that causes significant swelling from fluid retention, for decades and had undergone ten operations, including a leg amputation.

[61] Upon her return to the United States, five Boston-area physicians said that she was healed, and the case was declared miraculous by the Vatican in 1992 based on the additional testimony of over 20 witnesses about her prior condition.

On 5 October 1995, the feast day of the Blessed Faustina, Ronald Pytel allegedly collapsed consciously and was paralyzed when he venerated a relic of Kowalska and while a group was praying for his healing through her intercession at the Holy Rosary Church in Baltimore.

On 16 November 1999, after three years of examination of his case by doctors, the Congregation for the Causes of Saints declared that there was no medical explanation for the instant cure of his heart.