Earlier this year I needed an image of a working bee smoker*. But standard ambient light produced a rather flat image:

What to do? I hid a Canon 430EX speedlight out of view behind the smoker, and when it fired the smoke came alive:

Light does interesting things to smoke. I'm going to have to play with this more.

*The smoker is central to a beekeeper's toolkit, as bees remain calm and more easily worked in the presence of smoke.