A mechanism by which ice crystals grow from the vapour supplied by cloud droplets. In mixed clouds, where ice crystals and supercooled droplets coexist, the water vapour diffuses from supercooled droplets to ice crystals because the vapour pressure over ice is lower than over liquid water at the same temperature (Castellano et al. (2004) Atmos. Envir. 38, 39). See Korolev (2007) J. Atmos. Scis 64, 9 on the limitations of the Wegener–Bergeron–Findeisen mechanism in the evolution of mixed-phase clouds.