Metallic Wood Sample (IMAGE) University of Pennsylvania Caption A microscopic sample of the researchers' "metallic wood." Its porous structure is responsible for its high strength-to-weight ratio, and makes it more akin to natural materials, like wood. Credit University of Pennsylvania 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.