How to tie a woolly bugger when fly fishing

Streamers imitate food sources that swim. Nymphs are most often fished dead-drift at the same speed and direction of the current but streamers are usually fished on a tight line so they move like living creatures. From a fly-tying perspective, streamers should sink, have a relatively elongated profile, and be made of mobile materials that move and breathe with a life of their own.