High Speed Photography
When the ambient light is sufficiently low (or the shutter speed sufficiently high), the photograph gets exposed only in the very brief moment the flash lights up. For a typical flash, that’s between 1/2,000 sec and 1/16,000 sec. This makes it possible to photograph things that are not visible with the naked eye, such as a baloon popping or two water drops colliding in mid-air. It’s fun, some times a little messy, and in my mind quite pretty.