Interesting facts about the average distribution of matter in the universe can be found in the DISCOVER paper Taking the Measure of Nothing in the Universe (Corey S Powell, Feb 1 2017).
But very few of that mass is ordinary matter. Indeed, in the cited paper we read:
If you average out the entire cosmos, there is a total mass density of 9.9 x 10^-30 grams per cubic centimeter, which is equivalent to 5.9 protons per cubic meter. Note that I was describing mass density, however, not particle density. According to the latest data from the Planck satellite, only 4.8 percent of that density consists of ordinary matter, mostly hydrogen nuclei (protons). On average, then, there is 0.3 atoms per cubic meter of space.
Picture - Hubble Ultra Deep Field - from Wikipedia
