Twenty-seven years after raising $5,000 to support her desert-greening efforts, retired US teacher Ronald Sakolsky has reunited with Yin Yuzhen in China's Maowusu Sand Land. Where saplings once stood, a forest of over 50,000 trees now thrives. Watch as the duo plant new saplings and return to the very first tree they planted together in 2000. (Produced by Fan Liuyi, Ni Tao, Yu Xingxin, Geng Ziyun, Li Zhiyao, Zhao Jingfeng and intern Liu Hanqing)