Archaeologists have dug ancient pizza ovens out of the ash of Pompeii in southern Italy. But the classic pizza that we've come to know and love wouldn't exist without a little help from the New World. When the tomato was first brought to Europe from South America, the upper classes refused to eat it because they were convinced it was poisonous. But peasants were too poor to be picky, and they started spreading the red fruit on their pies. Several centuries later, fresh basil and mozzarella were added, and the classic pizza Margherita was born. Today, U.S. pizza toppings are as varied as the American palate. From pineapple to pickles, the only limit is your imagination.