Action shots: This tiny implantable device can continuously scan mouse brains as mice move freely. Many standard imaging devices rely on fiber-optic tethers and work best when mice are still.

Images courtesy of University of Arizona / GutrufLab

Small picture: A miniature microscope sits at the tip of the device, which can be made with common techniques used to manufacture consumer electronics.

Hidden halo: The lightweight device is implanted just beneath a mouse’s scalp without damaging brain tissue. Because it can recharge itself, it does not require heavy batteries that might impede the mouse’s movements.

Double vision: The implant (gold) can generate both magnetic resonance (blue) and computed tomography scans (gray).

Free run: Tracks from mice with the implant (gold) and those without (blue) are similar, suggesting the device does not alter the animals’ movements or behavior.

Task tracks: Mice with the implant (gold) and without it (blue) also perform similarly on common tasks, such as the elevated plus maze.