Students visit the Exhibition Hall of Evidences of Crime Committed by Unit 731 of the Japanese Imperial Army in Harbin, northeast China's Heilongjiang Province, Sept. 18, 2021. Unit 731 is a covert biological and chemical warfare research and development unit of the Japanese Imperial Army that undertook lethal human experimentation during World War II. Various activities are held on Sept. 18 in commemoration of the September 18 Incident 90 years ago that marked the start of Japan's 14-year invasion of China. (Xinhua/Wang Jianwei)
