Cheap wool often contains Acrylic fibers which do not biodegrade. These synthetic fibers can be easily distinguished under the microscope from natural wool from a sheep. Here I put different types of wool under the microscope. Specimen preparation is easy. All you have to do is put a small amount of cut wool on a microscope slide with a drop of water. Natural wool is thicker and has a surface texture. Synthetic fibers are much thinner.