Fluctuating Hydrodynamics and Rare-Event Techniques Unveil the Mesoscale Physics of Boiling

Deciphering the incipient stages of phase change in superheated fluids-and their subsequent evolution-remains a major challenge, as it requires bridging microscopic nucleation with macroscopic bubble dynamics and heat transfer. This gap has long hindered predictive boiling models and limited progress in emerging thermal technologies. Here, we leverage large-scale simulations of fluctuating hydrodynamics, combined with a rare-event technique, to rationalise liquid-vapour transformation from nucleation to bubble growth. We quantify the statistics of nucleated bubbles and hydrodynamic fields, onset temperatures, and non-trivial wettability effects on the nucleation pathways. Despite operating at the mesoscale, the simulations recover microscopic nucleation signatures observed in atomistic studies, including the dependence of both the boiling onset temperature and the crossover between homogeneous and heterogeneous nucleation pathways on surface wettability. At larger scales, they reproduce the experimentally observed transition from an early exponential regime of bubble-contact areas to a post-critical power-law scaling. These findings establish a quantitative bridge between fluctuation-driven nucleation and emergent boiling dynamics across scales.