Flash turns day into night.
In this photograph, a pair off-camera speedlights (that's Nikon-speak for strobe-light), hit the flowers with so much light that, by comparison, the background looks like nighttime, even though it's daytime: With flash, I can turn day into night. Like they do in the movies, sometimes.
[Spring arrives: Narcissus by the kitchen steps, 18 March 2010. Nikon 35mm f/2.0 lens on D700 camera with two (off-camera) SB-600 speedlights; exposure 1/125 s, f/22, ISO 800. Any trademarks are property of their respective owners; their appearance here is under fair use; no endorsement or sponsorship exists or is implied. The camera was hand-held against the ground; focus was set manually, using a wooden ruler to measure distance from the camera's sensor plane.]