The regions between superclusters, called voids, generally contain no galaxies.
Voids make up approximately 95 percent of the universe.
Contrary to what you may think, voids are probably far from empty.
Some astronomers believe that most of the matter in the universe resides in the voids, probably in the form of dark matter.
Dark matter is matter that is inferred to exist from gravitational effects on visible matter and background radiation, but is undetectable by emitted or scattered electromagnetic radiation.