What is 99% of all matter?

Most of the Universe Is Plasma—And You Probably Didn’t Know It

When we think of matter, we usually picture solids, liquids, or gases—the stuff we interact with every day. But in reality, 99% of all matter in the universe is plasma, a superheated, electrically charged state far removed from what we see on Earth.

Plasma might sound like science fiction, but it’s very much real. It forms when gas heats up so much that electrons break free from atoms, creating a swirling mix of ions and free electrons. This state isn’t common in our daily lives (except in neon signs or lightning), but it dominates the cosmos.

“About 99% of matter in the universe is plasma,” says Dr. Dennis Gallagher, a plasma physicist at NASA’s Marshall Space Flight Center. In fact, some estimates go as high as 99.9%. The reason? Almost all visible matter in space—stars, nebulae, and the vast interstellar medium—is made of plasma.

The Sun, for example, is a giant ball of plasma. So are all other stars. Even the space between stars isn’t empty; it's filled with thin, ionized gas—also plasma. On Earth, plasma is rare because our cooler environment favors solids, liquids, and gases. But beyond our atmosphere, plasma reigns supreme.

Despite being invisible to the naked eye in many cases, plasma plays a key role in phenomena like solar flares, auroras, and even the flow of energy through galaxies. Scientists study it not just to understand space weather, but also to develop fusion energy—one day potentially replicating the Sun’s power here on Earth.

So next time you look up at the night sky, remember: the twinkling stars aren’t just distant suns. They’re glowing beacons of plasma, making up nearly all the visible matter in existence. It’s not just the most common state of matter in the universe—it’s the universe’s default setting.