Rosetta Stone, theRoˈsetta Stone, the 
a large ancient stone that was found in Egypt in 1799, which had the same piece of writing on it in three different writing systems: Greek letters, Egyptian letters, and ancient Egyptian hieroglyphics. This important discovery made it possible for people to translate hieroglyphics for the first time. The stone is now kept in the British Museum. Something that could provide the answer to a problem, especially in a particular area of science, is sometimes called a Rosetta Stone: 
The study of genes in mice could be the Rosetta Stone for establishing the functions of human genes.
a large ancient stone that was found in Egypt in 1799, which had the same piece of writing on it in three different writing systems: Greek letters, Egyptian letters, and ancient Egyptian hieroglyphics. This important discovery made it possible for people to translate hieroglyphics for the first time. The stone is now kept in the British Museum. Something that could provide the answer to a problem, especially in a particular area of science, is sometimes called a Rosetta Stone: The study of genes in mice could be the Rosetta Stone for establishing the functions of human genes.