The mixing of festive sweetmeats and the stirring of cream into coffee are toothsome examples of the irreversibility of physical processes. In certain systems, however, the concept gets its just desserts

Rivers are the great conveyor belts that carry sediment from mountains to the sea. In the Punjab — the Land of Five Rivers — a wholesale shift occurred in the past that re-routed sediment to different oceans

Vertebrate embryos from fish to mammals seem to use different routes to work out which way is up and which side is front. Yet a novel system involved in defining the dorsal side of fish might be conserved in mammals