The silk that spiders use to build their webs, trap their prey and dangle from your ceiling is one of the strongest materials known. But it turns out it’s not simply the material’s exceptional strength that makes spider webs so resilient; it’s the material’s unusual combination of strength and stretchiness — silk’s characteristic way of first softening and then stiffening when pulled. These properties, scientists have found, vary depending on the forces applied, as well as on the overall design of the web. Professor Markus Buehler, graduate students Steven Cranford and Anna Tarakanova, and Nicola Pugno of the Politecnico di Torino in Italy find evidence of the key properties that make webs so resilient and relate those properties back to the molecular structure of silk fibers. Read a news release.