The Rosetta Stone is a granodiorite slab inscribed with a decree issued at Memphis in 196 BCE on behalf of King Ptolemy V. Because the decree is written in three scripts—Ancient Egyptian hieroglyphs, Demotic script, and Ancient Greek—it provided the essential key for modern researchers to decipher Egyptian hieroglyphs. It was discovered by French soldiers during Napoleon's Egyptian campaign in 1799. In 1822, Jean-François Champollion announced the final breakthrough in the decipherment, unlocking over 3,000 years of Egyptian history that had been unreadable for centuries. The stone has been held in the British Museum since 1802.