The papal conclave begins May 7. Here's how cardinals choose the next pope, what to expect and how secretive the process is.

One hundred and thirty-three cardinals are sequestering themselves behind the Vatican’s medieval walls for the start of a conclave to elect a successor to Pope Francis

A papal conclave is set to begin in Vatican City starting May 7, during which cardinals from around the world will elect the next leader of the Roman Catholic church. The tradition occurs any time a pope dies or resigns from the office. Pope Francis died April 21, the day after Easter.