Definitions of Inner Asia vary greatly. Inner Asia includes those lands that have linked the major agrarian civilisations of Eurasia, from China to India to the Mediterranean and Europe, since the late Neolithic period. In the 19th century, it became customary to refer to the trade routes between these regions as the 'Silk Roads'. But silk was just one of the goods exchanged through Inner Asia. religions, diseases, coins, cuisines, artistic fashions, political titles, all travelled the Silk Roads, as did Buddhism, Christianity, Manichaeism and Islam. Seen in this way, Inner Asia appears as the central knot in the vast tapestry of Eurasian history. To take Inner Asian history seriously is to see the underlying unity of Eurasian history.