Galaxies are like the nation-states of the universe. They are the civilized domains where most of the visible matter resides in cohesive structures of spirals or spheres. Stretching between them are vast no-man's lands where light could travel millions of years before bouncing off anything of substance.
Although we see galaxies all around us, and live inside one called the Milky Way, we are still far from comprehending the details of how galaxies are built, why they look and act as they do, and what their ultimate fates will be.
New discoveries enabled by ever more powerful telescopes are shedding light on these mysteries, and even raising a few more questions. Scientists hope that soon we will fully understand the nature of the Milky Way and its most distant relatives.