International audienceHazard assessment and definition of the eruptive scenarios at active volcanoes are mostly based on the elaboration of a large set of information collected with different disciplines and multiple analytical approaches. We discuss here how the reconstruction of the main processes acting at a volcano during its life should be based on the direct knowledge of its activity and products, in the view that each volcano is characterized by its own “personality.” Comparison with analogue volcanoes can add further important information on the expected variability of the different processes, but this should never substitute specific data collection at the volcano of interest. Field volcanology and petrology studies are the base fo...