Shallow-sea (<200 m depth) hydrothermal systems have garnered far less attention than their deep-sea or on-land counterparts. However, interdisciplinary research efforts on rock, sediment, water, gas, and biofilm samples collected in the Baia di Levante, Vulcano Island (Italy) have led to major discoveries in geobiology. For example, the archaeal species Pyrodictium occultum was the first isolated microorganism thriving at temperatures above 100°C, Aquifex and Thermotoga represent the highest temperature genera of Bacteria, and Archaeoglobus fulgidus was the first pure culture Archaeon capable of extracting metabolic energy from the reduction of sulfate to sulfide. In addition, the first large-scale assessment of in situ redox reaction energetics (potential catabolic strategies for chemolithotrophic Archaea and Bacteria) was carried out for the shallow-sea hydrothermal system at Vulcano. These and other fundamental contributions to our understanding of heat-loving (thermophilic) microorganisms in their natural habitats were facilitated by numerous detailed investigations of the aqueous geochemistry and volcanology of the Aeolian Islands.