It happens everyday on Facebook, Instagram and in real life—that moment when you see someone you haven’t seen in years. Maybe they’ve gone gray or gained a few pounds, but there’s no doubt you’re looking at that friend from high school or the cousin who moved away when you were both 10 years old. You see the boy you once rode bikes with in the face of the man or the girl who taught you how to French-braid your hair in the eyes of the woman.