It was exactly 315 years ago when French soldier Pierre-Francois Bouchard stumbled across a piece of rock in Egypt that had lots of writing on it. It turned out to be the most important slab of rock ever.
It contained the same text written in three different ways, in Egyptian hieroglyphics, common Egyptian and Greek, which was the primary language spoken in Egypt in 196 BCE, the time at which it was carved.
As scholars knew Greek but not hieroglyphics, they were slowly able to translate the hieroglyphics using the Greek words and then learn loads about Ancient Egypt from carvings on pyramid walls and other tablets. This took 23 years before Jean-Francois Champollion declared that he had broken the code in 1822.
It was named the Rosetta Stone because that was the English name of the town where it was found. It was locally known as Rashid.
Today it is the source of a number of disputes as it is currently sitting in the British Museum as its most popular exhibit, but the French, who found it, and the Egyptians, from whose country it is from, both want it returned.