The cardinals -- at least, those under 80 years old -- vote for as long as it takes to elect Pope Francis' successor.

A papal conclave, the election of a new pope, tends to begin 15-20 days after a papal vacancy. Black or white smoke indicates each day's decision.

The death of Pope Francis this month at the age of 88 set off grief and mourning around the world — along with a complex process to find a successor. Francis’ successor will be selected at a conclave that will begin May 7,