The Euclid mission aims to uncover the mysteries of the “dark” Universe. This ominous-sounding invisible part of the cosmos makes up more than 95% of the mass and energy in our Universe.

For centuries, astronomers have aimed to learn more about the luminous sources of the cosmos: planets, stars, galaxies, gas. But these objects make up only a small fraction of what the Universe contains.

95% of the Universe appears to be made up of unknown “dark” matter and energy. Scientists estimate that dark matter makes up 25% of the Universe and dark energy 70%. Dark matter and energy affect the motion and distribution of visible sources, but do not emit, absorb or reflect any light, and scientists do not know yet what these entities actually are. Understanding their nature is therefore one of the most compelling challenges of cosmology and fundamental physics today.