Pope Francis waved to the fervent crowd as he arrived to his installation Mass in St. Peter's Square.

Francis took part in his inaugural Mass in St. Peter's Square on Tuesday.

Among the hundreds of dignitaries in attendance was Vice President Joe Biden.

The fisherman's ring was placed on the finger of Pope Francis by Cardinal Angelo Sodano, dean of the College of Cardinals.

Nuns listened as Pope Francis read the gospel.

Cardinals attended Pope Francis's inaugural Mass.

During his inaugural Mass, Francis was interrupted by applause several times.

Priests lined up in St. Peter's Square.

Hundreds of thousands packed St. Peter's Square for the pope's installation Mass.

A priest delivered communion to the faithful in St. Peter's Square.

German Chancellor Angela Merkel attended the installation of the new pope.

French Prime Minister Jean-Marc Ayrault was among the world leaders who attended the Mass.

Zimbabwe's President Robert Mugabe and his wife Grace attended the Mass.

Spain's Prince Felipe (left) and Princess Letizia, and Spain's Prime Minister Mariano Rajoy (right) were in attendance.

Pope Francis waved to the crowd from an open-air vehicle.

Pope Francis arrived to his installation Mass.

Pope Francis got out of his vehicle to bless a disabled man prior to the Mass.

Many of the faithful took photos of Francis as he made his way through St. Peter's Square.

Pope Francis reached for a child during his tour through St. Peter's Square at the Vatican.

Argentines watched the inaugural Mass on a giant screen next to the Metropolitan Cathedral in Buenos Aires.

A woman held a sign as she watched the installation from Buenos Aires.

Faithful carried a Vatican flag as they waited to watch a broadcast of the inaugural Mass in Buenos Aires.

Argentina's President Cristina Fernandez de Kirchner, left, greeted Dutch Prince Willem-Alexander.

Chalices containing hosts were prepared before the Mass.

Nuns ran through St. Peter's Square to get a good vantage point.