President Barack Obama called himself a "great admirer" of Pope Francis as he sat down at the Vatican Thursday.
With the election of a new pope under way in Vatican City, here are 5 Things To Know About Electing a Pope:
1) The new Pope, the Bishop of Rome, will be elected by the College of Cardinals.
Cardinals are bishops and Vatican officials from all over the world, personally chosen by the pope. Their primary responsibility is to elect a new pope but they also serve as advisors to the pope. They are recognizable by their distinctive red vestments.
The cardinals convene in Vatican City to choose Pope Benedict XVI's successor in closed-door meetings called a conclave.
The cardinals take an oath of absolute secrecy and then meet in the Sistine Chapel totally cut off from the outside world. No TV. No newspapers. No computers. And definitely no cellphones.
2) Pope Gregory X established the conclave in 1274 after it took the cardinals two years and nine months to choose him as the successor to Pope Clement IV. Locking the cardinals in a meeting and gradually decreasing their food rations was seen as good way to prompt agreement on a new pope.
Over the centuries the system has changed. Food is no longer rationed, the cardinals meeting in the conclave are no longer locked in and one who arrives after the conclave begins can still be admitted.
3) A total of 115 cardinals will vote this week. A two-thirds majority (77 votes) is needed to elect a pope. If after 26 ballots a new pope still has not been chosen, a simple majority (50 percent plus one) becomes sufficient to choose the new pope under a decree by John Paul II.
One ballot may be taken on the first day of the conclave. Two morning ballots and two afternoon ballots may be taken on the following days.
The cardinals vote by secret ballot. Each cardinal writes his choice on a rectangular piece of paper inscribed with the words "Eligo in summen pontificem" - Latin for "I elect as Supreme Pontiff."
Holding the folded ballot up in the air, each cardinal approaches the altar and places it on a saucer, before tipping it into an oval urn, as he intones these words: "I call as my witness, Christ the Lord, who will be my judge that my vote is given to the one who, before God, I think should be elected."
After the votes are counted, and the outcomes announced, the papers are bound together with a needle and thread, each ballot pierced through the word "Eligo." The ballots are then placed in a cast-iron stove and burned with a special chemical mix – one that produces black smoke or one that produces white smoke – depending on the outcome of the vote.
4) The eyes of the world will be watching the 6-foot-high copper chimney atop the Sistine Chapel to pipe out puffs of smoke after each ballot.
Black smoke means "not yet" - the likely outcome after Round 1. White smoke means the 266th pope has been chosen.
When a cardinal receives enough votes for election, the dean of the College of Cardinals asks if he accepts his election. If he accepts, he chooses a papal name and is dressed in papal vestments. The senior cardinal deacon, currently French Cardinal Jean-Louis Tauran, then announces from the balcony of St. Peter's Basilica "Habemus Papam" ("We have a pope") and the new pope processes out to impart his blessing on the city of Rome and the entire world.
5) No choice is expected to emerge on the first ballot as a number of names have been advanced as possible frontrunners. Observers say the cardinal electors are split roughly into two groups -- those who wish to reform the Vatican's bureaucracy and are backing Italian Cardinal Angelo Scola and those who work at the Vatican and back Brazilian Cardinal Odilo Scherer, who has himself worked in the Curia, the administrative apparatus of the church in Rome.
Other contenders reportedly include Cardinal Gianfranco Ravasi, a Vatican insider, and Cardinal Marc Ouellet of Canada.
Pope Francis' pared down papal wardrobe of sensible black shoes and a white cassock so thin you can see his black trousers.
New surveys commissioned by the Vatican show that the vast majority of Catholics in Germany and Switzerland reject church teaching on contraception, sexual morality, gay unions and divorce, findings remarkable both in their similarity and in the fact that they were even publicized.
Two white doves that were released by children standing alongside Pope Francis as a peace gesture have been attacked by other birds.
A document obtained by The Associated Press on Friday shows Pope Benedict XVI defrocked nearly 400 priests over just two years for molesting children.
Benedict XVI has returned to the Vatican for the first time since he resigned Feb. 28 and met with successor Pope Francis.
Pope Francis put his humility on display during his first day as pontiff Thursday, stopping by his hotel to pick up his luggage and pay the bill himself.
Cleveland Bishop Richard Lennon and other area leaders react to the election of Pope Francis I.
Latin Americans are reacting with joy to news of the first pope from the hemisphere, bursting into tears and cheers.
Pope Francis is the first ever from the Americas, an austere Jesuit intellectual who modernized Argentina's conservative Catholic church.