Japanese harpsichord artist Yasuko Mitsui (1st L), also co-founder of Harmony for Peace Foundation, presents over 10,000 paper cranes held together by strings during her visit to the Museum of Evidence of War Crimes by Japanese Army Unit 731 in Harbin, capital of northeast China's Heilongjiang Province, Aug. 16, 2016. Unit 731 was a top-secret biological and chemical warfare research base established in Harbin in 1935 as the center of Japan's biological warfare in China and Southeast Asia during WWII. (Xinhua/Wang kai)