Clothing made of polyester, nylon or fleece gets softer and even comfier over time. It almost breaks down. That’s because when you wash this type of clothing, in a washing machine, thousands of the plastic fibers that make up the garment are shed into the water. They are extremely small, we’re talking five millimeters or less, and are called microfibers. They are too small to be caught by a washing machine’s filter and ultimately they end up in our waterways.