It all started with a mysterious photograph.
In 2011, Mary Gainer worked as a historic preservationist for Nasa, and she stumbled on a 1943 picture of a thousand people standing in a huge building.
Scattered here and there was something unexpected: Women, some white and some black, in knee-length skirts and pompadour hairdos. There were too many to be secretaries, so who were they?
Another person was on a similar hunt - only Margot Lee Shetterly was a step ahead. Shetterly's father was a scientist who worked at Langley, so growing up in the 1970s and 80s, she was aware of the history of black women at Nasa.
"I knew them, and my dad worked with them. They went to our church and their kids were in my school," she says. "It was my husband who was like, 'What is this story? How come I've never heard about it?' "