Pretty pictures: microscopic images. False-colour SEM (scanning electron microscope) pictures mostly, which are always entertaining. Do a Google image search for SEM and bug, insect, plant, pollen, whatever if you don't believe me. Viewing the universe from a completely different scale is always mind-blowing for me; completely unfamiliar images that still make perfect sense.

http://www.eyeofscience.de/eos2/index2.html