(CNN)She dedicated her life to helping the poor in India, performed several miracles and won a Nobel Peace prize in 1979.
Mother Teresa: How hard is it to become a saint?
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Mother Teresa, the world famous nun needs little introduction, and her canonization on September 4 at the Vatican in Rome, is expected to draw huge crowds.
But what exactly is a saint and how does someone become one?
We take a closer look.
A saint is a person who has lived a devout Catholic life, serving God and selflessly assisting people in need.
Saints act as role models and they're also believed to communicate with God on someone's behalf when a request for help is made in prayer.
Catholics believe a saint is someone who lived a holy life and who's already in heaven.
It's near impossible to figure out the exact number of saints. One well-known work called "Lives of the Saints" lists 2,565 Catholic saints, but that doesn't count thousands of others considered saints in other regions across the world.
The Catholic Church even has a feast, All Saints' Day, on November 1 to honor the countless saints who aren't formally canonized.
Most saints don't actively pursue sainthood.
Instead, they dedicate themselves to humanitarian tasks and devote themselves to God. In some cases, the Pope recognizes such goods deeds after the individual's death, first beatifying, then canonizing the person in question.
But you can't just be made a saint with the click of the Pope's fingers. There's a whole procedure -- described under the 'New Laws for the Causes of Saints' on the Vatican website -- that determines whether candidates really merit the honor, and the entire process can take several decades.
First up, a local church official examines a candidate's good deeds, life and writings for evidence of holiness and virtue. If they uncover enough material, they submit the candidate's case to the Vatican.
A group of cardinals and theologians of the Congregation for the Causes of Saints scrutinizes the case.
If the Congregation approves, the case is passed to the Pope. He decides if the candidate is "venerable" -- if they've sufficiently lived a life full of heroic Catholic virtue.
The next step is beatification -- recognition that an individual is in heaven. This status is granted when one of the candidate's miracles are verified posthumously. The miracle should be associated to prayers made to the candidate after their death from a person in need. If the prayer was granted, it proves that the candidate was able to communicate with God to conjure the miracle.
Miracles, however, are also scrutinized and deemed to be miraculous, only if they have no logical medical explanation.
The candidate is canonized and made a saint proper once a second miracle is verified posthumously.
The nun was beatified in October 2003 by now deceased Pope John Paul II. He approved a first posthumous miracle. A 30-year-old woman in Kolkata said she was cured of a stomach tumor after praying to Mother Teresa.
A Vatican committee said it could find no scientific explanation for her healing and declared it a miracle.
In March 2016, Pope Francis announced that Mother Teresa would be declared a saint after recognizing a second miracle attributed to her.
A Brazilian man with multiple brain tumors was healed after loved ones prayed to her, the Italian Catholic bishops' association's official newspaper Avvenire reported.