The Vatican announced on Monday that all 133 cardinal-electors eligible to choose Pope Francis’ successor have arrived in Rome, ahead of the highly anticipated papal conclave set to begin this week.

The conclave will formally commence on Wednesday, starting with a special Mass at St. Peter’s Basilica in the morning. Later that afternoon, at 4:30 pm local time (1430 GMT), the cardinals will proceed into the Sistine Chapel, where they will begin the secret voting process under Michelangelo’s iconic frescoes.

Voting will continue until one candidate receives a two-thirds majority, officially becoming the new leader of the world’s 1.4 billion Catholics. An initial vote is expected on Wednesday afternoon, followed by two rounds each morning and afternoon on subsequent days.

If no pope is elected after three days, the process will be paused for a full day of prayer and reflection, in accordance with conclave rules.

As per tradition, the only public indication of voting results will be the color of smoke rising from the chapel chimney: black for no decision, white to signal that a new pope has been chosen.