Foie gras is made from the liver of ducks or geese that have been deliberately overfed, producing fat accumulation in the liver. Migratory birds must gorge themselves in the wild in order store fat (in their liver and elsewhere) to use as energy during their long migration. This practice of fattening geese dates back to Egyptian times, or 3500 BC. A fresco from Saqqara depicts 6 Egyptians force-feeding geese, presumably in order to obtain this delicacy. The practice has continued in various parts of the world ever since.