Embroidery (xiu) has been practised in China for thousands of years. It typically uses a variety of stitch styles, and a wide range of time-honoured designs: figurative motifs depicting flowers, birds and animals, as well as geometric and abstract patterns. Untwisted (flat) silk threads create a rich sheen and, when combined with padded stitching, create wonderful three-dimensional effects; twisted threads are stronger and create bolder lines. Chinese embroidery has four distinct regional styles: Shu xiu (Sichuan), featuring mostly natural-world motifs; Su xiu (Jiangsu), in which colours are more naturalistic; Xiang xiu (Hunan), known for emulating paintings, engravings and calligraphy; and Yue xiu (Guangdong), characterised by the use of strong colours, no attempt to produce an illusion of depth, and a prevalence of dragons and phoenix motifs.