Born Agnes Gonxha Bojaxhiu in August 1910 in Skopje (in present-day Macedonia), the woman the world knew as Mother Teresa had by age 12 realized that she would spend her life aiding the poor. At age 18 she left her family to pursue that mission, joining a community of Irish nuns who were missionaries in Calcutta, India. There she took the name Sister Teresa and began teaching at St. Mary’s High School, which she would continue to do for the next 17 years. She took her final vows as a nun in 1937.

In 1946 she became ill and was believed to have contracted tuberculosis. Sent to Darjeeling in northeast India to recover, she was on a train when she “heard the call to give up all and follow him to the slums to serve him among the poorest of the poor.” In 1948 Pope Pius XII (1876–1958) allowed Sister Teresa to leave her order and pursue this mission. In 1950, after receiving some medical training, she founded the order of Missionaries of Charity in Calcutta. Two years later she opened a home for the dying poor (it was called Nirmal Hriday or “Pure Heart”). One year after that she opened her first orphanage. It was the children there who called her Mother Teresa, or sometimes simply “mother.”

She spent her life helping the sick and the outcast, who she described as “Christ in distressing disguise.” Small in stature, she was frail and in poor health in her final years, but she continued her work nevertheless. It was not until March 1997, just months before her death, that she finally stepped down as head of her order. Having started with only 12 members, the Missionaries of Charity had grown to include more than 4,000 nuns who continued to run orphanages and hospices around the world. Mother Teresa died on September 5 of that year. She was 87.