ROME - Tens of thousands of people filled St. Peter's Square this morning as the Pope held his final audience before resigning.

Pope Benedict XVI said goodbye to the crowds as the faithful waved banners saying "Thank You."

The pope acknowledged moments of "joy and light" during his papacy and also great challenges.

The pontiff talked about making difficult decisions for the good of the church.

Tomorrow he meets with cardinals and appears at his papal residence, then becomes the first pope in 600 years to resign.