It's show-and-tell time! Below are two movies I made using the volume rendering tools of yt. I've been using yt for a few years to analyze and visualize the cosmological simulations I make with Enzo, and only recently have I had time to begin to play with the new volume rendering stuff.
The first movie is a slow rotation around the entire volume of a simulation at a contemporary epoch, which means that this image is produced from the state of simulation at its end, 13 billion years after it started. The colors correspond to the density of matter in the volume, from dark blue to white as density increases. The simulation is a periodic cube with dimensions 20 Mpc/h on a side. In comparison, the diameter of our galaxy is somewhere around one thousand times smaller. This means that the whitest areas correspond to clusters of galaxies, and our galaxy would be just a small part of one of the white blobs. Be sure to watch the movie full screen!
Below shows the time evolution of the simulation from beginning to end. This is a thin slab of the center of the simulation (10% thickness) viewed from a corner of the cube. Notice that early on the matter is very clumpy everywhere, but rapidly forms dense knots connected by thin filaments. This is how the real universe looks! After about the half-way point of the movie you'll notice that not much happens. Again, this is how the real universe looks! Much of the large-scale evolution of the universe was finished about 7 billion years ago. This movie uses comoving coordinates, that compensate for the expansion of the universe. If I were to use proper coordinates, which are the kind we use every day to measure normal things with rulers, the movie would show the simulation starting very small and then blowing up. Again, use the full screen option for the best image.