Spider webs are incredibly strong and flexible. It’s no surprise, then, that spider silk proteins may someday form durable artificial ligaments for people who have injured their knees or shoulders. Six different kinds of silk are produced by orb-web weaving spiders. These silk fibers have very different mechanical properties that are so effective they have changed very little over millions of years. How to synthetically develop these silks is one focus of Lewis’ research. The secret to producing large quantities of spider silk is to use “factories” designed to manufacture spider silk proteins that are easily scale-able and efficient. Lewis uses transgenic goats, E.coli bacteria, transgenic alfalfa and transgenic silk worms to produce the spider silk proteins used to create spider silk. Spider silk is 100 times stronger than natural ligaments and 10 times stronger than natural tendons; it is stronger than Kevlar and more elastic than nylon.