Francis’ successor will be selected by cardinals at the conclave that begins on May 7. Cardinals, known as the “princes of the church,” rank just below the pope in the Roman Catholic Church; together, they are known as the College of Cardinals. When a pope dies, the college chooses a successor.

Jorge Bergoglio was 76 when he became Pope Francis. His predecessor, Joseph Ratzinger, was 78 when he became Pope Benedict XVI. The papacy wore him out enough that he resigned at age 85 — the first pope to voluntarily step down in 600 years.