One slab with the same decree in three scripts cracked a 1,400-year-old mystery

French soldiers rebuilding a fort near Rosetta in 1799 found a stone inscribed with the same royal decree in Egyptian hieroglyphs, Demotic script and Greek. Scholars could read the Greek immediately, but hieroglyphs had been unreadable since the fourth century AD. In 1822, Jean-François Champollion used the repeated royal names in oval cartouches to work out that hieroglyphs recorded sounds, not just ideas, finally unlocking the script.

— Jean-François Champollion, Rosetta Stone — Deciphered 1822