The Rosetta Stone is a dark granite stone (often incorrectly identified as "basalt") discovered in the Egyptian port city of Rosetta on July 15, 1799 by French Captain Pierre Bouchard during Napoleon's Egyptian campaign. Inscribed on it is a text in Egyptian and Greek, in two languages and three scripts - Egyptian hieroglyphicss, Egyptian demotic script and koine Greek. As Greek was well known, the stone was the key to deciphering the hieroglyphs in 1822 by Thomas Young and Jean-François Champollion. This led to the translation of other hieroglyphic texts.
The Rosetta Stone is on display at the British Museum in London, where it has been kept since 1802.
The same Ptolemaic decree of 196 BC is written on the stone in the three scripts. The Greek part of the Rosetta Stone begins: Basileuontos tou neou kai paralabontos tén basileian para tou patros... (The new king, having received the kingship from his father...) It is a decree from Ptolemy V, describing various taxes he repealed (one measured in ardebs (Greek artabai) per aroura), and instructing that statues be erected in temples and that the decree be published in the writing of the words of gods (hieroglyphs), the writing of the people (demotic), and the Wynen (Greek; the word is cognate with Ionian) language.Contents of text
Rosetta Stone is also used as a metaphor to refer to anything that is a critical key to a process of decrypting, translation, or a difficult problem, e.g., "the Rosetta stone of immunology", "thalamocortical rhythms, the Rosetta Stone of a subset of neurological disorders", "Arabidopsis, the Rosetta stone of flowering time".