Alternating mineral and protein layers give many sea creatures strong skeletons that can bend without cracking and withstand other underwater insults. Chemists have now used the same construction materials to build similar cylindrical, needlelike structures called spicules that are stronger and more flexible than the real McCoy. And they could be used to guide light in optical devices to boot. A team led by Wolfgang Tremel of Johannes Gutenberg University, in Mainz, Germany, mixed a solution of calcium chloride and a protein called silicatein-α found in sea sponge skeletons. They put the mixture under pressurized carbon dioxide gas to entice the formation of calcium carbonate and the subsequent growth of calcium carbonate-silicatein-α spicules (Science, DOI: 10.1126/science.1216260). The synthetic spicules (shown) have up to 16% protein content compared with the 1.5% found in sponges. The researchers suggest the increased protein content is responsible for the synthetic spicules’ remarkable flexibility, enabling them to sustain at least three times as much stress as natural spicules without any sign of fracturing.