Chip (IMAGE) University of Copenhagen - Niels Bohr Institute Caption The magnetic field sensor is made up of a glass container embedded with caesium metal. The caesium evaporates into gas at room temperature and the gas atoms rise up into the small channel in the sensor head. Each caesium atom is like a tiny bar magnet. Now the sensor is held close to a nerve, which emits an electrical nerve pulse. The electrical pulse has a magnetic field that causes a change in the tilt of the axes of the caesium atoms and by sending a laser beam through the gas, you can read the ultra-small magnetic fields of the nerve signals. Credit Kasper Jensen, NBI Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.