Waterproof adhesives and self-cleaning surfaces, mineralized teeth and hairy insect feet, the seemingly impossible-to-replicate awesomeness of spider silk: Here are a few of our favorite bio-inspired materials, and their natural sources.

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Normally soft and squishy, aquatic sea cucumbers can become rigid and tough when threatened. This reversible transition, from pliant to stiff, inspired a team of scientists at Case Western Reserve University to design a material with similar properties. But first, they had to learn how sea cucumbers accomplish the transition: A network of collagen fibers, strung within a soft matrix, stiffens when the animal secretes chemicals that cause the fibers to form bonds.