"E = mc2, equation in German-born physicist Albert Einstein’s theory of special relativity that expresses the fact that mass and energy are the same physical entity and can be changed into each other."
https://www.britannica.com/science/E-mc2-equation
"Dark matter makes up most of the mass of galaxies and galaxy clusters, and is responsible for the way galaxies are organized on grand scales. Dark energy, meanwhile, is the name we give the mysterious influence driving the accelerated expansion of the universe."
https://www.cfa.harvard.edu/research/topic/dark-energy-and-dark-matter
"But it is an important mystery. It turns out that roughly 68% of the universe is dark energy. Dark matter makes up about 27%. The rest - everything on Earth, everything ever observed with all of our instruments, all normal matter - adds up to less than 5% of the universe"
https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy
"Dark matter seems to outweigh visible matter roughly six to one, making up about 27% of the universe."
"Dark energy makes up approximately 68% of the universe and appears to be associated with the vacuum in space. It is distributed evenly throughout the universe, not only in space but also in time – in other words, its effect is not diluted as the universe expands."
https://home.cern/science/physics/dark-matter
"Dark matter, which makes up about 85% of the mass in the Universe, is more than simply dark."
https://www.lsst.org/science/dark-matter
"Astronomers estimate that roughly 85% of all the matter in the universe is dark matter, meaning only 15% of all matter is normal matter. Accounting for dark energy, the name astronomers give to the accelerated expansion of the universe, dark matter makes up roughly 27% of all the mass energy in the cosmos, according to CERN (the European Organization for Nuclear Research)."
https://www.livescience.com/how-much-dark-matter-universe
"Dark matter makes up about 85 percent of the total matter in the universe, accounting for more than five times as much as all ordinary matter."
https://www.energy.gov/science/doe-explainsdark-matter