The topic of the current Challenge, in the Canon Talk Forum on the Digital Camera Review web site, is Power.
Scratched my head to think of suitable images. The first thing that came to mind was the image of a steam engine belching steam and smoke – regrettable no longer an everyday event. So I had to fall back on a more mundane image, but nevertheless just as valid an example of power, and that is the power of nature. Small plants, which you can effortlessly squash between your fingers, force their way between cracks in the pavement (US sidewalk).