A polymer is a chemical compound with molecules bonded together in long, repeating chains. Because of their structure, polymers have unique properties that can be tailored for different uses.Polymers are both man-made and naturally occurring. Rubber, for example, is a natural polymeric material that has been used for thousands of years. It has excellent elastic qualities, the result of a molecular polymer chain created by mother nature. Another natural polymer is shellac, a resin produced by the lac bug in India and Thailand, which is used as a paint primer, sealant, and varnish. The most common natural polymer on Earth is cellulose, an organic compound found in the cell walls of plants. It is used to produce paper products, textiles, and other materials such as cellophane. Man-made or synthetic polymers include materials such as polyethylene, the most common plastic in the world found in items ranging from shopping bags to storage containers, and polystyrene, the material used to make packing peanuts and disposable cups. Some synthetic polymers are pliable (thermoplastics), while others are permanently rigid (thermosets). Still others have rubber-like properties (elastomers) or resemble plant or animal fibers (synthetic fibers). These materials are found in all sorts of products, from swimsuits to cooking pans.