The Persistence of Memory (1931) is perhaps surrealist painter Salvador Dali's most famous work. Recently, a student drew to my attention that the motif of droopy pocket-watches was suggested to Dali by a half-eaten Camembert cheese which had become soft. Dali is unlikely to have known the reason why white-mould cheeses such as Camembert become soft which, briefly, is due to deacidification of the cheese and migration of calcium phosphate towards its surface, both driven by metabolism of lactate by Penicillium camemberti. Of course, in Dali's case, the warm Catalan climate would have helped too...