Nikon has opened a re-review of the winner of its Small World in Motion competition after scientists publicly accused Dr Ning Xu of using artificial intelligence in his winning video.

The controversy centres on the prize-winning entry itself: a fluorescence microscopy video showing a layer of cells with long, green, hair-like cilia extending from their surfaces. It was this footage, credited to Dr Xu, that carried off the competition's top honour — and it is this footage that experts in the field now claim shows signs of AI generation or manipulation.

Nikon has confirmed it is "re-reviewing" the winning entry in response to the accusations. The competition, one of the most visible platforms for photomicrography and scientific imaging, now faces the uncomfortable question of whether its judging process can reliably distinguish genuine microscopy from machine-generated imagery.

The accusations came from scientists with expertise in microscopy, who flagged the video as likely containing AI-produced content. Their public challenge forced the competition's organisers to act rather than let the result stand unexamined.

At stake is more than a single prize. Small World in Motion has built its reputation over years as a showcase for genuine scientific imaging — work that demands patient laboratory technique, precise microscopy and often months of preparation. An AI-assisted or AI-generated winner would undermine the premise on which the contest's credibility rests.

For now, the green cilia that won Dr Xu the competition remain under scrutiny, and Nikon's re-review is ongoing. Its outcome — whether the award stands, is reassigned or prompts new verification rules — will signal how one of photography's longest-running scientific competitions intends to police the line between the microscope and the machine in future editions.