They’ve detected photons that traveled from one side of an adult human head to the other—an optical journey spanning over 15 centimeters and requiring passage through skull, brain, and bone.

For decades, brain imaging has been limited to either cheap but basic tools like EEG or expensive machines like fMRI that cost millions. Meanwhile, optical methods, which use light to measure ...

This could eventually lead to better tools for diagnosing and monitoring conditions like strokes, brain injuries, or tumors, especially in settings where access to MRI or CT scans is limited.