The Missionaries of Charity now has more than 4,500 nuns worldwide and is headquartered at the Mother House in central Kolkata.
In the city, the charity runs 19 homes - for women, orphans and the aged - where thousands of destitute people live. It also runs a school for street children, an Aids hospice and a leper colony.
Though the order's "service to the poorest of poor" has generated much appreciation worldwide, it's not without controversies.
The most recent controversy involves shutting down of its adoption centres in India.
The charity said it was forced to close the centres because India's new adoption laws, allowing single, divorced and separated couples to adopt, went against its religious views.