Rome (CNN) -- Pope Francis officially becomes the 266th Pontiff in an inaugural Mass held at the Vatican on Tuesday.
The ceremony at a glance:
St Peter's Square normally holds about 100,000 people
Vatican spokesman the Rev. Federico Lombardi says that if the Square and Via Conciliazione are full, the crowd is about 250,000.
There will be 132 delegations from around the world, including six reigning sovereigns and 31 heads of state.
Pope Francis's Fisherman's ring:
Pope Francis chose as his ring one with the figure of Peter holding the keys.
He chose it from two or three other possibilities. It is silver plated in gold. The jeweler is Italian artist Enrico Manfrini. The ring used to belong to Pope Paul VI's secretary.
It is a symbol of Episcopal authority. It is a long white wool scarf with five red crosses.
The pallium represents the good shepherd and the five crosses represent the five wounds of Christ.
The Pope's Coat of Arms:
Francis has decided to keep the same coat of arms and motto for papacy that he had as bishop of Buenos Aires, but will replace the cardinal's hat in the center with the papal hat and keys.
The coat of arms has a blue background, with HIS in the center, which signifies Christ but also Pope's membership to society of Jesus.
The coat of arms also has a yellow the flower of Nard, symbol of St Joseph, and a yellow star, symbol of Madonna.
The Pope's motto is "having had mercy, he called him"
Lombardi showed a picture of the coat of arms Monday's daily press briefing.