By Juliet Perry

(CNN) -- Hundreds of thousands of pilgrims are expected to gather in Rome to witness the canonization of Mother Teresa, the nun who dedicated her life to helping the poor in India.

The canonization mass, held by Pope Francis, will take place Sunday morning in St. Peter's Square in Vatican City. A number of bishops from both Albania, where Mother Teresa was born in 1910, and India are due to attend, as well as state leaders.

The crowd is anticipated to surpass the 300,000 that attended Pope John Paul II's beatification of Mother Teresa in Rome in 2003.

"Brothers and sisters, even in our days God inspires new models of sainthood," John Paul told the crowd at the time.

Speeding up sainthood

Most of the Catholic Church's saints or blessed people are honored decades, if not centuries, after their deaths. Traditionally, there is a mandatory five-year waiting period before formal evaluation of a candidate for beatification can begin.

Mother Teresa's devotees began pressing the Vatican soon after her death to speed up the nun's sainthood cause, saying her holiness was clear to many around the world. Pope John Paul II granted the special dispensation in 1999, and the procedure began.

The pope waived the waiting period in part, some believe, because of her fame and reputation.

John Paul II further paved the way for her beatification in 2002, when he approved a miracle attributed to Mother Teresa after her death.

The approved miracle involved Monica Besra, a 30-year-old Kolkata woman who said praying to the nun cured a stomach tumor. The Vatican committee said in October 2002 that it could find no "scientific explanation" for the woman's recovery.

"I took doctors' medicines, threw up and was in a lot of pain. But when I prayed to Mother Teresa from my heart, Mother Teresa blessed me and now I am healthy," Besra told CNN last week.

"My entire village and I am very happy that she is being made a saint."

Pope Francis formally announced that Mother Teresa would be declared a saint in March 2016, when he recognized a second miracle attributed to her.

A Brazilian man with multiple brain tumors was healed after loved ones prayed to Mother Teresa to heal him, according to Avvenire, a newspaper affiliated to the Catholic Church.

'Saint of the gutters'

Born Agnes Gonxha Bojaxhiu in 1910, Mother Teresa set up her Missionaries of Charity in the slums of Kolkata in 1950 and made her headquarters in the Indian city for nearly half a century.

Her small figure in a white-and-blue sari and sandals became familiar around the world. She died in Kolkata in 1997 at age 87.

Known as the "Saint of the Gutters" for her unending work and compassion for the poor, Mother Teresa was awarded the Nobel Peace Prize in 1979.

The Norwegian Nobel Committee said her spirit and the respect she had for the worth and dignity of human beings inspired constructive efforts to do away with hunger and poverty.

However, Mother Teresa's legacy has been criticized. Her critics say her charity isn't financially accountable and volunteers aren't properly trained. And some doctors claim Besra was healed by modern medicine, not by prayer.

The nuns and priests from the Missionaries of Charity continue her work around the world, including some ex-communist countries where she was banned. Her order has offices in Europe, Africa, the Americas and Australia, as well as Hong Kong and Russia.

A group of nuns will travel to the Vatican for the canonization ceremony, and those who remain in Kolkata will mark the day with prayers of thanks.

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