Concerns over Pope Francis' health have mounted in recent years as have questions about his succession. Here's what we know.

Time-honored rituals, drafted and refined over centuries, allow time for mourning and provide order at a dramatic moment of transition.

The combination of health issues has kept the Pope from performing his public duties, including weekly prayers on Sundays, but his doctors have recently said he is alert, joking, and continuing to work, as well as reading messages from well-wishers around the world.