Now, engineers at the Massachusetts Institute of Technology (MIT) have developed a new type of stretchy yarn that could help change that by making clothes much easier to recycle. Most stretchy clothing combines a spandex core with an outer layer made of polyester or nylon. As a result, most stretchy clothing is simply thrown away. They spun the material into yarn, melted it down, and spun it into new yarn ten separate times. Because the entire yarn is made from compatible polyethylene materials, it can be recycled without separating different fibers first.