I love the Nikon Small World Competition. Photographers send in images captured with light microscopes (that is, microscopes that rely on light, not ones that are easy to carry). I don't envy the judges, though, for having to choose between such amazing offerings.
Nevertheless, they do have to make their selections. So here's the 1st prize winner, a colonial diatom Chaetoceros debilis photographed by Wim van Egmond.
Personally, I found myself mesmerized by the 16th place 'spider with the parasitic wasp on its abdomen', taken by Geir Drange.
You can see the rest of the winners, honorable mentions and images of distinction here.