Until the first quarter if this century, it was commonly held that our galaxy, the Milky Way was the only one in the universe. Since Hubble’s discovery that some nebulae were galaxies in 1923, we have come to realize that our spiral galaxy is but one of many and that there are as many galaxies in this universe as there are stars in our own galaxy (100 billion roughly). Galaxies are not evenly and randomly distributed in space, but like all matter, they tend to group into larger, gravitationally linked systems, clusters. Some galaxy-rich clusters contain thousands of galaxies. Other poorer clusters, sometimes called groups, contain only a few. 

We live in such a galaxy poor cluster, the Local Group. It contains some thirty or so galaxies, of which only three are spiral galaxies, two giants: Andromeda (Sb) and the Milky Way (Sb), and one smaller spiral galaxy (M33). All the others are smaller, elliptical and irregular galaxies. Andromeda is some 2.2 million LY from us, and it and the Milky Way orbit a common center some 1.2 million LY towards Andromeda. In contrast, the Virgo cluster, a rich cluster over 50 million LY away in the direction of  the constellation Virgo, contains more than 2000 galaxies.
 

To the left, is a view of a 4 galaxy group.                   To the right, is a view of such a rich cluster, where every object is a galaxy

B. Superclusters 

From analysis of sky maps it is clear that rich and poor clusters form larger assemblages called superclusters which span hundreds of millions of LY. The supercluster to which we belong, called the Local Supercluster is centered on the Virgo Cluster and the Local Group is on the edge of this supercluster some 60 million LY out from its center. When we look at the patterns of how matter is arranged in the universe across distances of billions of light years, superclusters seem to be spaced some 400 million LY apart, separated by large volumes of space with few, if any, galaxies: voids.
This view of a universe populated by galaxies holds across time and space. Below are two views of deep space taken by the Hubble Space Telescope. They record some of the most distant galaxies ever imaged.
 

To the left is a view of deep space in the direction of the North Celestial Pole.   To the right is a view of deep space towards the South Celestial Pole.