Look around you, and chances are high that a variety of the things you can see are made of plastics. There are hard plastics and soft plastics, clear ones and colorful ones, and plastics that look like leather, wood, or metal. Developed during the twentieth century, plastics have changed the world.
Plastics are synthetic materials, which means that they are artificial, or manufactured. Synthesis means that "something is put together," and synthetic materials are made of building blocks that are put together in factories.
The building blocks for making plastics are small organic molecules - molecules that contain carbon along with other substances. They generally come from oil (petroleum) or natural gas, but they can also come from other organic materials such as wood fibers, corn, or banana peels! Each of these small molecules is known as a monomer ("one part") because it's capable of joining with other monomers to form very long molecule chains called polymers ("many parts") during a chemical reaction called polymerization. To visualize this, think of a single paper clip as a monomer, and all the paper clips in a box chained together as a polymer.