In the Émosson region (Canton of Valais, Swiss Alps), a paleontological treasure was discovered at an altitude of 2400 m. On a sandstone slab, footprints left by animals 240 million years ago were unveiled in 1976 during an exceptionally warm summer that melted the snow covering the footprints. What animals could have left these traces, in what environment did they live and why are these footprints visible today in Émosson? Tamara El Hossny and Lionel Cavin, both paleontologists at the Natural History Museum of Geneva, answer these questions and show us all the secrets contained in these fossilised footsteps.