This was the winner, the head of a fish with a fluorescently-tagged skeleton. It's comprised of 350 images, and it formed part of research that revealed zebrafish also have lymphatic vessels. Previously only thought to be found in mammals, their discovery could help with research into human brain diseases like Alzheimer's.
“By studying [zebrafish] now, the scientific community can expedite a range of research and clinical innovations – everything from drug trials to cancer treatments. This is because fish are so much easier to raise and image than mammals.”