As part of its ongoing series ‘Darkroom,’ Vox has published a video showing how the work of photographer Lewis Hine helped bring to light the injustice of child labor across the United States.

The roughly seven-minute video not only shows the meticulous work of Hine, but also contextualizes the significance of his photography, which was captured at a time when 1.75 million children aged 10–15 were at work in factories, mines, plantations and other dangerous work environments. In total, more than 5,000 photographs were captured, each of which is accompanied by a detailed caption of its subject(s).

It’s a brilliant breakdown and well worth a watch. You can find more videos from Vox’s ‘Darkroom’ series on Vox’s YouTube channel.