Which is the main ingredient of an omelette?

In cuisine, an omelette (also spelled omelet) is a dish made from beaten eggs, fried with butter or oil in a frying pan (without stirring as in scrambled egg). It is quite common for the omelette to be folded around fillings such as chives, vegetables, mushrooms, meat (often ham or bacon), cheese, onions, or some combination of the above. Whole eggs or egg whites are often beaten with a small amount of milk, cream, or water.

Source: Wikipedia