Pope Francis died Monday at the age of 88. As tributes pour in from around the world, the Vatican faces a transition.

A new pope will be selected to lead the Catholic Church following the death of Pope Francis. The pope is chosen during a highly secretive election called a conclave. Francis, 88, died on April 21. The pope will be honored with a nine-day mourning period known as the Novendiale, a tradition that began in Ancient Rome.