Toucan Beak (image) University of California - San Diego Caption The interior of the toucan's beak is rigid "foam" made of bony fibers and drum-like membranes sandwiched between outer layers of keratin, the protein that makes up fingernails, hair and horn. The result is solid "foam" made of air-tight cells that gives the beak additional rigidity. Like a house covered by a shingled roof, the foam is covered with overlapping keratin tiles, each about 50 micrometers in diameter and 1 micrometer thick, which are glued together to produce sheets. Credit Marc Meyers/Jacobs School of Engineering, UC San Diego Usage Restrictions Credit required 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.