Deadliest Volcanoes

Millions of people around the world live in the shadow of active volcanoes. Under constant threat of massive volcanic eruptions, their homes and their lives are daily at risk from these sleeping giants. From Japan's Mount Fuji to the "Sleeping Giant" submerged beneath Naples to the Yellowstone "supervolcano" in the United States, we will travel with scientists from around the world.

NOVA brings you to selected volcanoes to see how they work and when they will erupt.