Francis’ successor will be selected by cardinals at the conclave that began 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.

Catholic cardinals are returning to the Sistine Chapel on Thursday for a second day of voting to try and elect a new pope . The 133 cardinals are expected to vote again in the morning after spending the night sequestered at the Vatican residences.

Catholic cardinals will sequester themselves Wednesday behind the Vatican’s medieval walls for the start of a conclave to elect the 267th pontiff of the Roman Catholic Church, a successor to Pope Francis who died in April at the age of 88.

Catholic cardinals from around the world gathered in the Vatican on Wednesday for the start of the conclave, the centuries-old secret voting ritual to elect a new pope to follow Pope Francis, who died April 21.