Varied Structure for Added Strength (IMAGE) University of Copenhagen - Faculty of Science Caption A heavily enlarged 3-D print of the sea urchin shell in cross section reveals the secret to the immense strength of the calcium shell of the sea creature. Dirk M&uuml;ter, Assistant Professor at the Department of Chemistry, University of Copenhagen, discovered that hundreds and thousands of tiny struts criss-cross the material making the sea urchin shell more air than calcium. Credit Jes Andersen/ University of Copenhagen. 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.