Have you ever been stung by anemones, jelly fish or fire coral and wondered how such a painful sting can come from such a harmless looking creature? The answer is nematocysts (nem–uh-tuh-sist). These are syringe-like organelles that are used to inject venom into the body of its prey. When activated, they deliver the venom into your skin at an average of 11 milliseconds!
Check out this video uploaded by Destin Christian at Smarter Every Day that explains this in great detail as well as high speed camera captures of the nematocysts at work!