Wool fibres. Scanning electron micrograph (SEM) of wool fibres from an Aran garment. Wool is chiefly obtained from the fleece of the domesticated sheep. Wool is differentiated from hair by the numerous, pointed scales which can be seen covering the outside of each fibre. Wool fibres are strong and elastic, which gives woollen fabrics the ability to retain their shape. Woollen garments are also characterized by their lightness, their ability to absorb moisture and their insulating properties. The value of wool on the world market depends primarily on the fineness and length of the fibres. Magnification: x340 at 5x7cm size. Magnification: x775 at 6x4.5 inch size.