You could be forgiven for thinking that the smile has no history; it has always been the same. However, just as different cultures in our own day have different rules about smiling, so did different societies in the past. In fact, amazing as it might seem, it was only in late eighteenth century France that western civilization discovered the art of the smile. In the ''Old Regime of Teeth'' which prevailed in western Europe until then, smiling was quite literally frowned upon. Individuals were fatalistic about tooth loss, and their open mouths would often have been visually repulsive. Rules of conduct dating back to Antiquity disapproved of the opening of the mouth to express feelings in most social situations. Open and unrestrained smiling was associated with the impolite lower orders. In late eighteenth-century Paris, however, these age-old conventions changed, reflecting broader transformations in the way people expressed their feelings. This allowed the emergence of the modern smile par excellence: the open-mouthed smile which, while highlighting physical beauty and expressing individual identity, revealed white teeth. It was a transformation linked to changing patterns of politeness, new ideals of sensibility, shifts in styles of self-presentation - and, not least, the emergence of scientific dentistry. These changes seemed to usher in a revolution, a revolution in smiling. Yet if the French revolutionaries initially went about their business with a smile on their faces, the Reign of Terror soon wiped it off. Only in the twentieth century would the white-tooth smile re-emerge as an accepted model of self-presentation. In this entertaining, absorbing, and highly original work of cultural history, Colin Jones ranges from the history of art, literature, and culture to the history of science, medicine, and dentistry, to tell a unique and untold story about a facial expression at the heart of western civilization.