The upper part of this combo photo shows seven-year-old Zhou Ning reading at her home in Jiagedaqi District of the Greater Hinggan Mountains area, northeast China's Heilongjiang Province. Behind her was cavity wall where hot air moved through so as to heat up room in winter. The lower part of the combo photo taken by Wang Kai shows 44-year-old Zhou Ning reading at home. Zhou now works at a power supply company. She moved from her previous small house into a new house in 1990s. Her family now enjoys the heating system in winter. (Xinhua)