The human brain beats just like the heart, scientists have discovered.
The tiny movements, which are smaller than the width of a human hair, have been caught on film for the first time.
The discovery could lead to better ways of spotting concussions and other brain injuries before they become life threatening.
It also offers hope of developing cycling and motorbike crash helmets that provide better protection.
The US team used a revolutionary imaging technique to capture and magnify the movement of the brain every time the heart beats - in real time.