Right off YouTube. A fantastic, entertaining clip of a white blood cell chasing and engulfing a bacterium. Students enjoy watching a live cell move close up. You can use it to teach the immune system, or just introduce students to the cell. I used it today in class to show students how big eukaryotes (white blood cell) is compared to prokaryotes (bacteria). Also, I talked about cell specialization (blood cells--"ghosts" vs. white blood cells). They loved it!