Today's state-of-the-art nylon carpet fiber is the result of nearly 70 years of continuous research and development. In the late 1920's, U.S. scientists began to experiment with giant molecules or "polymers" that resembled natural fibers such as cotton and wool. They discovered that these polymers are actually comprised of many small molecules linked together in a long chain. They named their discovery "nylon" and soon began to construct different chains of their own. Each chain was given its own name according to the number of carbon atoms in its molecular structure. The first nylon developed was nylon 6,6. From the 1930's onward, other types were created for various uses, including nylons 3, 4, 6, 7, 11 and 12. Although the latest type, nylon 46, was introduced in 1984, the two basic types of nylon used in contract carpet today are nylon 6,6 and nylon 6.