Pope Benedict XVI's resignation sets in motion a complex sequence of events.
- The Vatican summons a conclave of cardinals that must begin 15-20 days after Benedict's Feb. 28 resignation.
- Cardinals eligible to vote - those under age 80 - are sequestered within Vatican City and take an oath of secrecy.
- Any baptized Roman Catholic male is eligible for election as pope, but only cardinals have been selected since 1378.
- Two ballots are held each morning and two each afternoon in the Sistine Chapel. A two-thirds majority is required. Benedict in 2007 reverted back to this two-thirds majority rule, reversing a 1996 decision by Pope John Paul II, who had decreed that a simple majority could be invoked after about 12 days of inconclusive voting.
- Ballots are burned after each round in a fireplace in the Sistine Chapel. Black smoke means no decision; white smoke signals that cardinals have chosen a pope and he has accepted.
- The new pope is introduced from the loggia overlooking St. Peter's Square with the words "Habemus Papam!" (Latin for "We have a pope!") and he imparts his first blessing.