A microscope the size of a matchbox is allowing US biologists to peer inside the brains of live animals.

Weighing a mere 3.9 grams, the microscope has been used to image blood vessels lying 1 millimetre below the surface of the brains of anaesthetised mice, with a resolution of 1 micrometre (one-thousandth of a mm).

The researchers believe they may one day be able to view brain cells in the same way. In future the tiny microscope could be strapped to the head of a conscious, moving animal and beam back a movie of the neurons while the animal engages in a variety of activities, say its creators, led by Mark Schnitzer of Stanford University, US.

“It’s a microscope that fits in the palm of your hand,” says co-creator Ben Flusberg. It could also be a quick, easy way to image diseased or tumour-laden brains, which currently require an MRI scan or large machinery, he says. Or it could pave the way for a mobile, pocket-sized diagnostic tool.

But it is not clear whether the device would ever be used in humans because of its invasive nature. “It’s an ingenious device, but whether it’s transferable from mouse to man is not mentioned,” says Britton Chance, a biophysicist at the University of Pennsylvania, US, who focuses on non-invasive imaging.

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