Visitors view exhibits during a preview of "By the Light of the Silvery Moon: A Century of Lunar Photographs" at the National Gallery of Art in Washington D.C., the United States, on July 9, 2019. Some 50 works including a selection of photographs will be displayed in the exhibition lasting from July 14, 2019 through Jan. 5, 2020 to mark the 50th anniversary of the Apollo 11 moon landing. (Xinhua/Liu Jie)