A staff member introduces how special glass is applied in aerospace field to pupils of Haigang District Beihuanlu Primary School in Qinhuangdao, north China's Hebei Province, April 24, 2019. Since 2016, China has set April 24 as the country's Space Day. The various activities on Space Day have become a window for the Chinese public and the world to get a better understanding of China's aerospace progress. (Xinhua/Cao Jianxiong)