Wu Jinjuan, 9, and Wu Siyu, 5, sisters from Guilin, embark on a long journey to be reunited with their migrant worker parents who labor in Guangdong province, about 100 km from Guilin, July 9, 2014. Summer vacation, for some left-behind children, means a precious reunion with parents who work far away from their home towns. [Photo/CFP] Read More: Bittersweet reunion for left-behind children