A teacher introduces the correct sleeping posture for children at a kindergarten in Weinan City, northwest China's Shaanxi Province, March 21, 2017. Tuesday marks the World Sleep Day. (Xinhua/Cui Zhengbo)
A teacher introduces the correct sleeping posture for children at a kindergarten in Weinan City, northwest China's Shaanxi Province, March 21, 2017. Tuesday marks the World Sleep Day. (Xinhua/Cui Zhengbo)