Volunteers serving as delegation guide attend the opening ceremony rehearsal of the 2014 Nanjing Youth Olympic Games in Nanjing, capital of east China's Jiangsu Province, on August 12, 2014. According to the Local Organising Committee, there are about 20,000 volunteers, most born in the 1990s, playing different roles in spectator services, competition services, medical services, food services, IOC members services, etc. with their vigor and hospitality. (Xinhua/Yan Yan)