In total, matter – the stuff from which humans and objects on Earth are made – makes up around a third of the total matter and energy in the universe.
If it was spread out across the space in the universe, it would mean just six hydrogen atoms per cubic meter, says study author Mohamed Abdullah, a graduate student at the University of California, Riverside.
The research was published in the Astrophysical Journal.
But 80% of that is dark matter, a mysterious form of matter which is still not fully understood, says Abdullah.
Read more: yahoo