Surely the best-kept secret in human history was that of silk production, the subject that we are going to look at today. The Chinese were able to prevent outsiders from discovering the process of manufacturing silk for about 3000 years, until around the third century CE. It was such a lucrative product that its trade led to the east—west route we now know as the Silk Road. But a process so profitable could not stay a secret forever; eventually, the outside world learned that silk was made from silkworm cocoons. What had scientists scratching their heads for the next 700 years was how a worm could produce such an incredibly tough and resilient material. Silkworms spin strands of thread around themselves in lengths of up to one kilometre. Once their cocoon is complete, it is so strong—five times stronger than steel, in fact—that it is almost impossible to make a dent in it. Unfortunately for those wishing to exploit this material, the silkworm cannot be rushed. The worm must be kept in exacting conditions and fattened up for a month on mulberry leaves before it is ready to spin its thread. A modern economy cannot tolerate this kind of time constraint and the quest to synthesize silk became a pressing one. It wasn't until 1999, however, that progress was made. An American geneticist at the University of Wyoming decoded the DNA of a silk gene, paving the way for the commercial production of synthetic silk.