Guests and student representatives attend the opening ceremony of the 30th China Adolescents Science and Technology Innovation Contest in south China's Hong Kong, Aug. 20, 2015. The contest kicked off on Thursday. A total of 34 teams representing 31 provinces, municipalities and autonomous regions nationwide, Hong Kong and Macao special administrative regions, Xinjiang Production and Construction Corps (XPCC) and over 500 adolescents from 12 foreign countries including Germany, Sweden, India and Brazil will compete and exchange ideas during the four-day-long contest. (Xinhua/Qin Qing)