Claude Hopkins created "Reason-Why Advertising" which, as David Ogilvy later wrote, "perceived the importance of brand images a generation before the term came into use." Hopkins told Americans that Quaker Puffed Rice and Puffed Wheat were "Shot from guns" and advised them to "Brush the film" off their teeth with Pepsodent. His greatest contribution to advertising was his insistence that all copy be tested. He later laid out his principles in his still influential Scientific Advertising.