As the conclave to elect the next pope begins Wednesday at the Vatican, four candidates have emerged as clear favorites—Cardinals Pietro Parolin, Luis Antonio Tagle, Matteo Zuppi and Pierbattista Pizzaballa.

As more than a billion Catholics around the world await the election of a new pope, all eyes will be on the Sistine Chapel, where 133 cardinals will begin the secretive process known as a conclave.