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.

As more than a billion Catholics around the world await the election of a new pope, all eyes will be on the Sistine Chapel, where 133 cardinals will begin the secretive process known as a conclave.