(president of the Hong Kong University of Science and Technology) marked the issue of the special stamps by personally stamping the first day cover. The Four Great Inventions was featured as one of the main themes of the opening ceremony of the 2008 Beijing Summer Olympics. Paper making was represented with a dance and an ink drawing on a huge piece of paper, printing by a set of dancing printing blocks, a replica of an ancient compass was showcased, and gunpowder by the extensive firework displays during the ceremony. A survey by the Beijing Social Facts & Public Opinion Survey Center found that Beijing residents found the program on the Four Great Inventions the most moving part of the opening ceremony. Other important inventions Other significant innovations were made, however they are not included among the top four. Silk and porcelain were the most important for world profit and the growth of the various empires' economy. They were valuable commercial items exchanged along the Silk Road routes, and when the processes for producing them were understood in Europe and the Islamic world, large businesses grew in both. See also Dream Pool Essays History of science and technology in China List of Chinese inventions Science and technology of the Han dynasty Technology of the Song dynasty Notes References History of science and technology in China Chinese inventions