Good question! The answer, THIS week, is "galaxies".
However, we don't know how much hydrogen there is in intergalactic space; for all we know, there's more free hydrogen between the galaxies than there is in all the stars. Alternatively, we might argue that most of the matter has already fallen into various black holes, or exists in some impossible-to-detect "dark matter". We know a tiny fraction of one-thousandth of one percent of everything that we need to know - and discovering all those answers will be the work of the next several thousand years.
Open Clusters
Planetesimal formation.
Clusters of algae are called Colonies.
the clusters are called ganglions
There are 35 galaxies in the so-called "Local Group" The three largest galaxies are the Milky Way (our own), and the Andromeda and Triangulum galaxies. However, most of the visible stars we see are part of the Milky Way and two nearby dwarf galaxies, the "Small Magellanic Cloud" and the "Large Magellenic Cloud". There are 10 other dwarf galaxies near the Milky Way.
It's called a mat. Or matted hair.
Clusters
Open Clusters
Planetesimal formation.
They are called "Star Clusters".
Clusters of algae are called Colonies.
Two consonants together are called a consonant cluster. In English, consonant clusters can be found at the beginning, middle, or end of words.
The Universe
its not the universe it's called a cluster.
A so-called "great wall", which is a block of galaxies more than a billion light-years long.
A collection of galactic groups form a cluster of galaxies. A supercluster is the largest known structure. Galaxies can exist outside of a group or cluster, but the estimated amount is only about 5%. However, there is a possibility that these galaxies may have interacted or merged with other galaxies in the past,
Those are called globular clusters, or star clusters.