Light-Guiding Hydrogel Implant (IMAGE) Massachusetts General Hospital Caption Light passing through an optical fiber (left) can either carry in a signal that stimulates the activity of cells embedded in the hydrogel implant or bring back a signal generated by cells responding to something in their environment. Credit (Harvard Bio-Optics Lab/Wellman Center for Photomedicine, Mass. General Hospital) 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.