Watch: The conclave that confused everyone
The conclave - the secret process to elect the new pope - begins on 7 May.
Inside the Sistine Chapel the cardinals will vote until a new pope is elected, with each round marked by a traditional smoke signal.
Black smoke signals the conclave has not yet come to a decision, and white smoke tells waiting crowds that a new pope has been chosen.
In 1958, the smoke led to widespread confusion when crowds saw white smoke - only for it to turn black moments later.
The BBC looks back at archive footage from 1958 to piece together what happened on that day.
Video produced by Sofia Ferreira Santos.
