PhD Comics does a wonderful job of explaining of sub-atomic particles: what we know, what we don’t know. What’s particularly great about this video is that it goes into how physicists are using the Large Hadron Collider to try to discover new particles: by making graphs of millions of collisions of particles and looking for the tiniest of differences between different predictions of what might be there.
I also like how clear they make the fact that science is a processes of discovery, and what fascinates scientists is the unknown. Students do experiments all the time and if they don’t find what they expect — if it “doesn’t work” — they’re usually very disappointed. I try my best to let them know that this is really what science is about. When your experiment does not do what you want, and you’re confident you designed it right, then the real excitement, the new discoveries, begin.