Nano-sized bubbles (IMAGE) Penn State Caption Nano-sized bubbles allow macrophages to stand out from their fellow cells in ultrasound imagery. Credit Jennifer M. McCann/Materials Research Institute/Penn State Usage Restrictions Credit must be given to the creator. Only noncommercial uses of the work are permitted. No derivatives or adaptations of the work are permitted. License CC BY-NC-ND 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.