It is also the largest publicly held corporation by market capitalization, at $501.17 billion on April 18, 2008. Exxon's reserves were 72 billion oil-equivalent barrels at the end of 2007 and are expected to last over 14 years.

While it is the largest of the six oil giants with daily production of 4.18 million BOE (barrels of oil equivalent) in 2007, ExxonMobil is 14th in the world when ranked by held oil and gas reserves. Rex W. Tillerson is the chairman and CEO of ExxonMobil. ExxonMobil reported sales to the tune of $358.60 billion and profits stood at $40.61 billion in 2007.

Exxon Mobil Corporation was formed in 1999 by the merger of two major oil companies, Exxon and Mobil. Both Exxon and Mobil were descendants of the John D. Rockefeller corporation, Standard Oil which was established in 1870.

In 1911, the Supreme Court of the United States ruled that Standard Oil must be dissolved and split into 34 companies. Two of these companies were Jersey Standard (Standard Oil Company of New Jersey), which eventually became Exxon, and Socony (Standard Oil Company of New York), which eventually became Mobil.

Image: ExxonMobil Chairman Rex Tillerson. | Photograph: Brian Harkin/Getty Images