This combination photo shows glove maker at work in Macao, south China (top, photo by Tang Mengzong, issued on Aug. 30, 1986) and a student doing experiment on traditional Chinese medicine in a national-level lab at the University of Macao in Macao, south China on Oct. 30, 2019 (bottom, photo by Liu Jinhai). On Dec. 20, Macao will celebrate the 20th anniversary of its return to motherland. Over the past two decades, the special administrative region has made great strides in economic development and achieved prosperity and stability under the "one country, two systems" principle. Since Dec. 20, 1999, the historic day for Macao, what has changed? And what remains unchanged? Our selection of photos present comparative illustrations of the south China city's past and present. (Xinhua)