A new class of biomolecules called magneto-sensitive fluorescent proteins, or MFPs, could improve imaging of biological processes inside living cells and potentially underpin innovative therapies. The fluorescent proteins commonly used in biological studies respond solely to light being shone at them. But because that light gets scattered by tissues there are inaccuracies in determining exactly where the resulting fluorescence originates. By contrast, the MFPs created by a team led by Harrison Steel, head of the Engineered Biotechnology Research Group at the University of Oxford in the UK, fluoresce partly in response to highly predictable magnetic fields and radio waves that pass through biological tissues without deflection. **Sensor schematic** An MFP excited by blue light emits green fluorescence, the intensity of which can be modulated by applying appropriate magnetic or radiofrequency fields.…