Matter is defined, according to General Relativity, as a massively condensed form of energy. This property allows for the conversion of a tiny amount of matter into energy to provide power, both in a controlled electricity-generating form and a destructive uncontrolled form, as the citizens of Hiroshima well know.

Matter also has the property, explained by Albert Einstein, of warping space around it. This topographic manipulation is perceived by us as the force of gravity. .

All known interactions in the universe occur between matter and energy, or any combination of the two, and thus an understanding of both would basically constitute a theory of everything. The closest thing, presently offered, to a theory of everything is superstring theory, which claims that the fundamental particles we know of are actually only larger manifestations of Plank-length sized oscillating strings.