Polyester fabric is a synthetic fabric; it's completely man-made and not derived from a plant or an animal. The polyester fiber is made by heating petroleum and gas to form solid chips. These chips are melted and spun into a thread-like fiber. A machine with a winding tube twists the fibers to add stretchiness and elasticity, and then the yarn is woven into fabric. While polyester is inexpensive to produce, is easy to clean and resists stretching, wrinkles and mildew, it also has its downsides. Polyester batting for quilts and pillow filler is less expensive than down, but unlike down, it tends to flatten out and clump over time. As a petroleum-based product, it also has a wide range of negative impacts on the environment. The good news is that several companies are now making polyester thread from recycled plastic bottles instead of petroleum — as in this pillow from Design Public.