Dark Matter

Dark matter is a hypothetical type of matter distinct from dark energy, baryonic matter and neutrinos. The name refers to the fact that it does not emit or interact with electromagnetic radiation, such as light, and is thus invisible to the entire electromagnetic spectrum. Although dark matter has not been directly observed, its existence and properties are inferred from its gravitational effects such as the motions of visible matter, gravitational lensing, its influence on the universe's large-scale structure, on galaxies and its effects in the cosmic microwave background.

Reference: https://en.wikipedia.org/wiki/Dark_matter