In the course of our 170 year relationship, photography has delighted us, served us, moved us, outraged us and occasionally disappointed us. But mainly, it has intrigued us by showing the secret strangeness that lies beneath the world of appearances. And that is photography's true genius.
Follow the story of photography in BBC Four's six-part series 'The Genius of Photography'. See some of the most famous photographs ever taken and find out more about what made them so very special.