Retired US teacher Ronald Sakolsky says his time in China changed him for the better. During a visit 27 years ago, he met Yin Yuzhen and helped raise $5,000 to support her fight against desertification in North China, an amount equivalent to about 20 years of her income at the time. With no machinery, Yin and her husband planted tens of thousands of trees by hand. Decades later, Ronald still shares her story, calling her "a true hero." (Produced by Fan Liuyi, Yu Xingxin and Geng Ziyun)