One of the things I took away from university was an interest in jellyfish, thanks to a term paper I wrote on the creatures. Their nematocysts in the cnidae (stinging cells) are especially fascinating because of the way such complex structures developed in a single cell.
For the first time, the discharge of a nematocyst has been recorded, using a camera that takes 1.4 million frames a second. The article below links to a video clip!
New Scientist Breaking News - Explosive sting of jellyfish captured on film