Conclave: How a pope is elected - PHOTOS

When the conclave begins on Tuesday, the cardinal electors -- those under the age of 80 -- will meet in the Sistine Chapel, sleep in special apartments within Vatican City and have no contact with the outside world. (Source: SOURCES: Matthew Bunson, editor of "The Catholic Almanac;" the Rev. Thomas Reese, author of "Inside the Vatican: The Politics and Organization of the Catholic Church." Jerry Mosemak, Janet Loerhke and Cathy Grossman, USA TODAY)