Polymers are everywhere. Just look around. The silicone rubber tips on your phone’s earbuds .Your plastic water bottle. The nylon and polyester in your jacket or sneakers. The rubber in the tires on the family car. Now take a look in the mirror. Many proteins in your body are polymers, too. Consider keratin (KAIR-uh-tin), the stuff your hair and nails are made from. Even the DNA in your cells is a polymer.

By definition, polymers are large molecules made by bonding (chemically linking) a series of building blocks. The word polymer comes from the Greek words for “many parts.” Each of those parts is scientists call a monomer  (which in Greek means “one part”). Think of a polymer as a chain, with each of its links a monomer. Those monomers can be simple — just an atom or two or three — or they might be complicated ring-shaped structures containing a dozen or more atoms.

Wool, cotton and silk are natural polymer-based materials that have been used since ancient times. Cellulose, the main component of wood and paper, also is a natural polymer. Others include the starch molecules made by plants. [Here’s an interesting fact: Both cellulose and starch are made from the same monomer, the sugar glucose. Yet they have very different properties. Starch will dissolve in water and can be digested. But cellulose doesn’t dissolve and can’t be digested by humans. The only difference between these two polymers is how the glucose monomers have been linked together.

Polymers touch almost every aspect of modern life. Chances are most people have been in contact with at least one polymer-containing product — from water bottles to gadgets to tires — in the last five minutes.

Even more-sophisticated technology uses polymers. For example, “the membranes for water desalination, carriers used in controlled drug release and biopolymers for tissue engineering all use polymers,” according to the ACS.

Popular polymers for manufacturing include polyethylene and polypropylene. Their molecules can consist of 10,000 to 200,000 monomers.