Cotton plants grow, and the cotton is harvested from the plants. Then it is separated from the seeds and made into threads. The threads are then woven into cloth. Denim is different from your cotton shirts in the way that it is woven, which makes it stronger and longer lasting. Before talking about Spandex and polyesters, we should talk about polymers.
Polymers are a class of chemicals that are often known as plastics.
Most chemicals are made of small particles called molecules, and these molecules are made of atoms, the smallest particles of matter. Polymers are special because they have long chain molecules, much larger than most molecules. They are formed from smaller molecules that combine to form chains, like people holding hands to make a chain of people. The molecules tangle like strands of spaghetti, giving special properties. Spandex is a type of polyurethane, a class of polymers which is also used for foam cushions.