Editor’s Note: In Snap, we look at the power of a single photograph, chronicling stories about how both modern and historical images have been made. CNN  —  The photograph could have been taken at any birthday party: three girls in dresses standing side-by-side in a living room, balloons and streamers strung up around an entryway. The subjects could be friends or sisters, each with long brown hair that falls past their waists. But with their faces turned away from the camera, there’s a reason