At the beginning of the 20th century, the U.S. had a major child labor problem. The children were working in mills, fields, mines and factories, and the statistic says that one in five children under 16 were working at this time. But one photographer’s work helped to put this to an end. In this video from Vox, you’ll hear the story of Lewis Wickes Hine. His powerful images of child workers from the early 20th century contributed to the end of child labor in the United States.