Volcanoes have terrified and, at the same time, fascinated civilizations for thousands of years. Many aspects of volcanoes, most notably the eruptive processes and the compositional variations of magma, have been widely investigated for several decades and today constitute the core of any volcanology textbook. Nevertheless, in the last two decades, boosted by the availability of volcano monitoring data, there has been an increasing interest in the pre-eruptive processes related to the shallow accumulation and to the transfer of magma approaching the surface, as well as in the resulting...