Classifying dogs into categories began with the Romans. They had the following 6 categories: house dogs, shepherd dogs, sporting dogs, war dogs, dogs that ran by scent, and dogs that ran by sight. Interestingly enough, Mosaics meaning "Beware of the Dog" could even be found on doorsteps in ancient Roman cities. Today, more than three hundred breeds of dogs exist worldwide. The American Kennel Club recognizes 148 breeds which are classified into 7 categories: Terrier, Working, Sporting, Hound, Herding, Toy and Non-sporting.