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.

The conclave, which will kick off on Wednesday, will be held behind the closed doors of the Sistine Chapel. It generally lasts several days and, in some cases, weeks. The term conclave comes from the Latin term “con clavis”, meaning “with a key”, a reference to the tradition of locking the cardinals away until a new pope is elected.

There are currently 135 cardinals who are under age 80 and eligible to vote in the conclave, hailing from 71 different countries in the most geographically diverse conclave in history. Already two have formally told the Holy See that they cannot attend for health reasons, bringing the number of men who will enter the Sistine Chapel down to 133.