Once the conclave starts, all eyes will be on the smoke at the Vatican.
Black smoke means no pope has been chosen and white smoke means Habemus Papum, or "we have a pope." And yes that chimney will have its own twitter account: @PapalSmokeStack.
The cardinals will announce the start of the conclave this afternoon. After a week of pre-conclave meetings, the secret vote to elect a new pope is expected to go more quickly than in past years.
When the conclave begins, the cardinals will meet first for mass at St. Peters Basilica then head into the Sistine Chapel for the actual voting process. The magic number will be 77, the number of votes needed to be elected, or two-thirds of the 115 electors.
While they are "in conclave" at Casa Santa Marta there is much secrecy. Telephones and televisions will be disconnected and the location has been swept for eavesdropping devices. The cardinals will "draw lots" to guarantee objectivity and show no one has decided who is next to whom.
The cardinals can go to each other for confession. There also will be priests available to them.