As the Canton Fair marks its 70th anniversary, more than 30,000 exhibitors and around 340,000 overseas buyers are expected to attend the event. Over the years, the fair has witnessed the rapid upgrading of China's trade scale. CGTN reporter Zheng Songwu has been walking the exhibition halls since the 140th edition opened on October 15th. His mission is to find out why international buyers keep returning year after year.