Water

The most unusual compound known to science is water. The liquid form is denser than the solid form, and it is the only known compound that is naturally found in the three most basic states of matter. It is also made up of oxygen and hydrogen, two elements that are known to react violently. An example is that liquid oxygen and liquid hydrogen are used to create rocket fuel. Also, water is now the basis of the celsius scale, with water freezing at roughly zero and boiling at roughly 100.

-H20