Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 143.For thousands of years man has marvelled at the gigantic structure that makes up Mt. Etna, the largest active volcano in Europe, and has lived side by side with the mountain, which despite its intense eruptive activity has always been considered a “friendly giant.” After the Second World War, with its frequent but non life-threatening eruptions, Mt. Etna represented an ideal location for volcanological research for the national and international scientific community. Numerous scientists from Belgium, Germany, France, the United Kingdom, and the United States of America have taken part in volcanological research aimed at understanding the volcano.