When a Pope dies the Catholic Church's most important priests, called cardinals, all travel to Rome. One of them will almost certainly be the new leader.
They go to the old Pope's funeral and then after nine days they start to elect a new Pope.
The voting is very secretive and there are lots of odd traditions.
- Each cardinal gets one vote.
- A person can only become the Pope if they get more than two thirds of the votes cast by the cardinals.
- If after 30 rounds of voting the cardinals still have not picked a new Pope, then anyone getting more than half the votes can become pope.
The results are sent to people outside the Vatican using smoke signals.
- Black smoke means the cardinals haven't made up their minds yet.
- White smoke means they have chosen a new Pope. The bells in the church of St Peter's Basilica will also ring.