Composite (IMAGE) DOE/Pacific Northwest National Laboratory Caption When calcium carbonate crystallizes into hard shells, it incorporates soft bits of proteins to add strength. Research done in the lab shows how this might happen, and why it works. Credit <a target="_blank"href="https://en.wikipedia.org/wiki/Calcium_carbonate#/media/File:Calcium_carbonate_chunks.JPG">Wikipedia</a> Public Domain Usage Restrictions None, <a target="_blank"href="https://commons.wikimedia.org/wiki/File:Calcium_carbonate_chunks.JPG">Public Domain</a> 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.