These glowing neurons might look like an alien forest at night, but you're actually seeing inside a mouse’s brain

Dozens of glowing blue neurons against a black background, their teardrop-shaped cell bodies trailing long, thread-like branches that run vertically through the frame like a forest of tangled trees. — (Image credit: Kaelin Wulf and Rachel Flannery, Allen Institute, courtesy of Nikon Small World)

Glance at this image without context, and you might imagine a forest of trees on an alien planet. In fact, you’re looking at the neurons inside a mouse’s brain.

This stunning image, by Kaelin Wulf and Rachel Flannery of the Allen Institute in Seattle, took third place in the Nikon Small World 2026 Photomicrography Competition. And the way they captured it is utterly remarkable.

Neurons, aka nerve cells, are the fundamental working units of the brain and nervous system. They use chemical and electrical signals to receive, process and transmit information around our minds and bodies.

Neurons in an expanded mouse brain

As you can imagine, neurons are very tiny indeed, and the branches connecting them are tinier still. So small they’re hard to separate even with a conventional light microscope.

To photograph them, then, the team at the Allen Institute – a non-profit that carries out large-scale research into the brain, cells and the immune system – couldn't just rely on magnification alone.

Instead, they used a technique called expansion microscopy. Quite simply, this means physically enlarging the tissue by embedding a sample of the brain in a special gel that makes it swell like a balloon.

Wulf and Flannery also used two other techniques.

The first was fluorescence, which makes the labelled neurons glow, so they stand out vividly against the dark. The second was light sheet imaging, which involves scanning the sample with a thin plane of light, and building up a sharp, 3D picture slice by slice.

By combining all these techniques, the image could then be photographed using a modest 5X objective lens. The resulting image? Both scientifically useful and stunningly beautiful.

Nikon Small World showcases the beauty and complexity of life as seen through the light microscope via photography and video, and is open to anyone with an interest in microscopy.

This year’s overall winner was Ole Bielfeldt’s never-before-seen view of an inkjet printer at work. You can view all the winning images on the Nikon Small World website.

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Tom May is a freelance writer and editor specializing in art, photography, design and travel. He has been editor of Professional Photography magazine, associate editor at Creative Bloq, and deputy editor at net magazine. He has also worked for a wide range of mainstream titles including The Sun, Radio Times, NME, T3, Heat, Company and Bella.