Two thousand years ago the Greeks burned oil in their lamps and the Chinese and Egyptians heated their homes with it, but the day of oil's real importance didn't begin until the middle 1800s.
In 1859 a group of investors near Titusville, Pennsylvania, got tired of just collecting the little bit of oil that rose to the surface of the earth, so they hired Edwin Drake to find a better way to get at it.
Drake drilled a hole into the ground, and first try, hit oil. The world has not been the same since.
From oil we get fuel for all types of vehicles, as well as thousands of by-products such as asphalt, plastics, paints, medicines, lubricants, etc.
Scientists believe the world's oil supply was formed when tiny, ancient plants and animals died and were subjected to tremendous pressures under tons of rock. This downward pressure tended to force the oil up until it was trapped under a solid rock barrier.
Currently, Saudi Arabia and Kuwait have the greatest known oil reserves, with the Soviet Union in third place.
With its vast number of petroleum-powered vehicles, the industrialized world imports huge amounts of this oil, which has both advantages and disadvantages.
On the one hand, there are mutually beneficial economic ties created between the industrial world (which gets a relatively inexpensive source of energy) and oil producers (who receive great wealth by selling their oil). But on the other hand, burning oil causes pollution and may make the industrialized world too dependent on unstable parts of the world. And for the producing countries, such as Saudi Arabia, the influx of wealth and foreigners may disrupt traditional social structures.
