On SundayPope Franciswill declare Blessed Teresa of Kolkata — Mother Teresa — a saint at a canonization service tobe held in front of St. Peter’s Basilica in Vatican City. Here are five facts you should know about the nun who became renownedfor serving the poor:

1.Mother Teresa was born Anjezë Gonxhe Bojaxhiu in 1910 in what is now part of modern Macedonia. At the age of 18 she left home to join the Sisters of Loreto, a group of nuns in Ireland. It was there she took the name Sister Mary Teresa after Saint Thérèse of Lisieux. A year later, in 1929, Mother Teresa moved to India and taught at a Catholic school for girls.In 1946 Mother Teresa received what she would later describe as a “call within a call.” She said Jesus spoke to her and told her to abandon teaching to work in the slums of Calcutta aiding the city’s poorest and sickest people. In 1950 she received Vatican approval for Missionaries of Charity, a group of religious sisters who took vows of chastity, poverty, obedience, and to give “wholehearted free service to the poorest of the poor.” By the late 1970s, the Missionaries of the Charity had offshoots in Asia, Africa, Europe, and the United States.

2. Mother Teresa and her religious order gained international attention in 1967 when the famed journalist Malcolm Muggeridge interviewed her for a BBC TV program. Because of the popularity of the interview, Muggeridge traveled to Calcutta a year later to make a documentary, Something Beautiful for God, about Theresa’s “House of the Dying” (Muggeridge would also write a book by the same name in 1971).

3. During her life Mother Teresa received more than 120 prestigious awards and honors.In 1971, Paul VI conferred the first Pope John XXIII Peace Prize on Mother Teresa, and in 1979 she won the Nobel Peace Prize. The Norwegian Nobel Committee writes in their motivation: “In making the award the Norwegian Nobel Committee has expressed its recognition of Mother Teresa’s work in bringing help to suffering humanity. This year the world has turned its attention to the plight of children and refugees, and these are precisely the categories for whom Mother Teresa has for many years worked so selflessly.” She also received the highest U.S. civilian award, the Presidential Medal of Freedom, in 1985.

4. Mother Teresa was frequently denounced by secularists because of her opposition to contraception and abortion. But she was also widely criticized for her allowing her charity to provide inadequate care for the poor and for potential mismanagement of charitable funds. Although she leveraged her fame to raise tens of millions of dollars for her charity, the orphanages and care centers run by her religious order were often substandard. After visiting Mother Teresa’s Home for the Dying in 1994, Robin Fox wrote about the experience in the British medical journal, The Lancet. Fox reported that doctors only occasionally visited the patients (the care was mostly provided by untrained volunteers) and that pain relief provided for the dying was inadequate, leading them to suffer unnecessarily. In 2008, another observer reported, “I was shocked to see the negligence. Needles were washed in cold water and reused and expired medicines were given to the inmates. There were people who had chance to live if given proper care.”

5. For Mother Teresa to be recognized as a saint within the Catholic Church, she had to undergo the lengthy process of beatification and canonization. The process usually cannot be started until 5 years after the person has died, but Mother Teresa received a waiver from Pope John Paul II. Before beatification (which recognizes the person’s ability to intercede to God on behalf of individuals who pray in his or her name) a person must have a verified miracle attributed to them after their death. After beatification the Church looks for a second miracle before proceeding to canonization. If one is found and they meet the other criteria, the pope can conduct a special mass at which the person is recognized a saint. The first miracle attributed to Mother Teresa involved the healing of an Indian woman, Monica Besra, whose abdominal tumor was so severe that her doctors abandoned hope of saving her. After a Miraculous Medal that had been touched to the body of Mother Teresa was placed on Besra’s stomach, the tumor reportedly disappeared. The second miracle involved a Brazilian man who reportedly was healed of a bacterial infection in the brain after he and his family prayed to Mother Teresa for her help.