Although it sounds hard to believe, everything we see with the naked eye or through microscopes and telescopes accounts for just 4 percent of the known universe. The rest comprises dark energy (69 percent) and dark matter (27 percent). Although there seems to be more dark matter than visible matter in the universe, we still have not been able to directly detect it. The reason is that dark matter does not emit light or absorb electromagnetic waves, so it is really hard to observe. Interestingly, dark matter is needed to explain the motions of galaxies and some of the current theories of galaxy formation and evolution. For example, the galaxy that contains our solar system, the Milky Way, seems to be enveloped by a much larger halo of dark matter; though invisible, its existence is inferred through its effects on the motions of stars and gases.