<p id="internal-source-marker_0.36668464934399725" dir="ltr"><strong>What looks like a tangle of Christmas lights is actually the <a href="http://science.nationalgeographic.com/science/health-and-human-body/human-body/brain-article/">brain</a> of a zebrafish embryo, winningly photographed for the <a href="http://www.nikonsmallworld.com/">2012 Small World Microphotography Competition</a>.</strong></p><p dir="ltr">Winners of the international contest were announced Tuesday. This shot—taken by Jennifer Peters and Michael Taylor of <a href="http://www.stjude.org/stjude/v/index.jsp?vgnextoid=f87d4c2a71fca210VgnVCM1000001e0215acRCRD">St. Jude Children's Research Hospital </a>and magnified 20 times—took first prize. It's believed to be the first image ever to show the formation of the blood-brain barrier in a live animal.</p><p dir="ltr">The barrier is a protective system of cells that filter the blood that flows to the brain. It allows nutrients and other necessities to pass but keeps out bacteria and other pollutants.</p><p dir="ltr">To create this shot, Peters and Taylor injected fluorescent proteins into a transparent zebrafish embryo. That let them see the brain's endothelial cells—which line the inner surface of blood and lymphatic vessels—and watch the development of a blood-brain barrier in real-time.</p><p dir="ltr">Their three-dimensional image was made with a confocal microscope, which colors blood vessels differently at different depths. (Confocal lenses capture light from a single plane of focus, rather than all available light.) Peters and Taylor stacked their colored images and compressed them into a single shot to show the complexity of the phenomenon they witnessed.</p><p dir="ltr">(See <a href="http://news.nationalgeographic.com/news/2011/10/pictures/111006-nikon-small-world-microphotography-competition-science/">pictures of 2011's best micro-photos</a>.)</p><p>—<em>Kate Andries</em></p>