Pizza is an ancient culinary tradition that goes all the way back to a flat bread the ancient Babylonians made in mud ovens using unleavened bread. These original recipes are very similar to today's pizza crust recipes. The ancient Greeks improved on this flat bread by adding assorted toppings such as olive oil, herbs, and other toppings called plankuntos. Ancient Egyptians incorporated flat bread sprinkled with herbs into traditional celebrations for the Pharaoh's birthday. The ancient Romans also favored this delicious flat bread. Mozzarella cheese, a key ingredient in modern pizza, was first developed from the milk of Indian water buffalos in the seventh century. Mozzarella was introduced into the Italian diet by the 1700's with invasions from Asian armies. Another critical ingredient, tomatoes, were first brought to Europe from Peru and Mexico in the 1500's. At first, Europeans were sure that tomatoes were a deadly poisonous fruit - however, this fear was quickly overcome by brave daredevils, and the tomato went on to become a staple of the southern European, particularly Italian, diet. Greek and Italian peasants continued to partake of the flat bread developed by the ancients. Peasants in Naples, Italy developed the more modern type of pizza using ingredients such as wheat flour, olive oil, lard, cheese, and herbs. By the 1800's pizza was a popular fast food, and Naples was reknown for offering the best pizza. Street vendors, typically young boys, took their pizza to the streets wearing small tin stoves as a type of hat to keep the pizza warm. Antica Pizzeria Port'Alba, the world's first pizzeria, opened in Naples in 1830, and is still in business to this day. In 1889, Rafaele Esposito of the Pizzeria di Pietro e Basta Cosi (now called Pizzeria Brandi) baked a patriotic-looking pizza for the visit of King Umberto I and Queen Margherita using red tomato sauce, white mozzarella cheese and green basil leaves (the colors of the Italian flag). Queen Margherita loved the pizza, and what eventually became Pizza Margherita has since become an international standard. Pizzeria Brandi, now more than 200 years old, still proudly displays a royal thank-you note signed by Galli Camillo, "head of the table of the royal household", dated June 1889. Italian immigrants brought pizza to the United States in the 1800's. An immigrant named Gennaro Lombardi opened the first American pizzeria in 1895 in New York City. Since then, pizza has become one of the most popular meals in the United States, with countless variations.