I have always been impressed by how smooth the rings of Saturn look like. But the rings are actually made up of small chunks of ice, and sharp-eyed users at the Unmanned Spaceflight.com forum noticed that thousands of small boulders and moonlets were casting shadows on the ring, reminding us that the ring is not just one huge solid thing. It helps that the Sun is now lower on the horizon from the viewpoint of the rings, which means that longer shadows are cast.
The Cassini spacecraft just tweeted about what it sounded like when it arrived at Saturn and passed through the ring plane in 2004. While the spacecraft did not fly through the visible rings, there seems to be enough dust forming an invisible ring where it passed through to pelt the spacecraft with a lot of dust. These must have been truly microscopic dust, since if they were big enough to be visible enough to be seen by the naked eye, they would probably have destroyed the spacecraft at the speeds it was traveling.