* Most of the visible universe's mass is in the form of dark matter. Dark matter is a mysterious substance that doesn't interact with light, making it invisible. We know it exists because of its gravitational influence on visible matter.

* Of the visible matter, the vast majority is hydrogen and helium. These elements make up stars, planets, and interstellar gas.

* Only a small fraction of the visible universe is made up of heavier elements, like oxygen, carbon, nitrogen, etc. These are formed inside stars through nuclear fusion.

So, while hydrogen and helium make up the majority of the visible matter, the vast majority of the universe's mass is in the form of dark matter.