Agent 1 (image) Rice University Caption An electron microscope image shows bismuth ions (dark lines) sitting inside carbon nanotubes. The material created at Rice University is a contrast agent that may allow clinicians to track the progress of stem cells in the body with a CT scanner. Credit Eladio Rivera/Rice University Usage Restrictions None 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.