Where does energy from oil come from?

Step 1 - Energy Capture

Side view of a typical diatom, the energy-trapping organism generally thought to be the origin of oil.

In spite of some popular misconceptions, oil doesn't come from dead dinosaurs. In fact, most scientists agree that oil comes from creatures the size of a pinhead. These one-celled creatures, known as diatoms, aren't really plants, but share one very important characteristic with them - they take light from the sun and convert it into energy. (Humans can't do this - this is why you have to eat your veggies!)

Diatoms float in the top few meters of the oceans (and lakes, for that matter - which is part of the reason why not ALL oil comes from ocean deposits!) and also happen to be a major source of food for many forms of ocean swimmers. Their skeletons are chemically very similar to sand - in fact, they are made of the same material (silica). Diatoms produce a kind of oil by themselves - both to store chemical energy from photosynthesis and to increase their ability to float. But this small amount of oil still needs to become concentrated and mature before it can be taken from the ground and used as fuel.