The Pizza began simply as a garnished flat bread sold by roaming vendors to the poor in the streets of 18th century Naples. Probably the biggest step wards its present-day persona was the acceptance of the tomato by the Neapolitans, and the subsequent use of its flesh as pizza topping.
This happy culinary partnership was endorsed, so the story goes, in 1889 when queen Margherita was
accompanying her Husband, Umberto I of Savoia on an inspection of his Italian Kingdom. During her trips around the kingdom she saw many peasants and poor people eating a flat bread which they called "Pizza".The curious queen summoned her guards and asked them to bring her a piece of this flat bread. The queen liked what she ate and would eat this flat bread every time she went out of her palace.
The queen was extremely popular with the masses and had developed a great liking for their Pizza. This taste was considered somewhat undesirable in court circles. One day in June, on the queens insistence Raffaele Esposito was summoned from his pizzeria to the palace to bake a selection of Pizzas for the queen.
Raffaele in order to honour the queens desire for his
pizzas baked a special pizza with tomato, Mozzarella, cheese and basil (the colours of the Italian flag - red/white/green). The pizza was a great hit with the queen and Esposito was summoned often to bake this pizza. When the news got out that the queens favourite was topped with tomato, mozzarella & basil, she not only became an even greater hit with the public, but also started a trend for the Pizza Margherita that has lasted in Naples and around the world to this day.
http://www.chefexpress.com/history.htm