When I was younger, we used to get Ranger Rick magazine. One of my favorite parts of the magazine was the back page. It contained a grid of mystery photos. Each small square had an extreme close-up of an organism and you could try to guess which organism it came from.
Here's one for you to try! (The answer is below the photo.)
If you guessed the underside of a fungus or mushroom, you're right! The following are all different views of the same fungus on a eucalyptus tree photographed today. I'm asking a friend for help with the identification, so will report back with more information soon.
ADDENDUM (28 August 2012): Peter and Brendan have both suggested that this is Laetiporus sulphureus (Sulphur Shelf or Chicken-of-the-Woods). Thanks for the identification assistance!