Sure, this is old, but I hadn’t seen a video quite this cool before. Behold, a human polymorphonuclear leukocyte (PMN, or neutrophil) on a blood film, “chasing” Staphylococcus aureus.
There are more videos of cells in action here.
It never ceases to amaze me how cells can detect biochemical gradients over such short distances and use them for navigation. I’m sure I’ll find it just as fascinating right up until the day I can’t think of science anymore.