Yarn is a long continuous length of interlocked fibres, suitable for use in the production of textiles, sewing, crocheting, knitting, weaving, embroidery, and ropemaking. Cotton and polyester are the most commonly spun fibers in the world. Cotton is grown throughout the world, harvested, ginned, and prepared for yarn spinning. Polyester is extruded from polymers derived from natural gas and oil. Synthetic fibers are generally extruded in continuous strands of gel-state materials.