 The city has an international flair, with about 7,500 foreign students and researchers from as many as 133 countries living in Tsukuba at any one time.Over the past several decades, nearly half of Japan's public research and development budget has been spent in Tsukuba.Important scientific breakthroughs by its researchers include the identification and specification of the molecular structure of superconducting materials, the development of organic optical films that alter their electrical conductivity in response to changing light, and the creation of extreme low-pressure vacuum chambers.