In the northern part of the Tibetan plateau, and in the south along the northern slope of the Himalaya, nomadic herdsmen still provide most of the thick, lustrous wool for which Tibet is famous. This ready supply of high-quality wool, together with the cold climate and an industrious Tibetan population, led to the production of rugs for domestic and monastic use. Often these simple, elegant rugs were made in conditions of relative poverty, by women who passed their skill on from mother to daughter. Sometimes carpets were woven by two women, as seen from the lighter and darker shades of blue in a single carpet, for example. Colour variations were also due to the fact that the people dyed the wool themselves using natural dyes such as indigo, imported from India, and it was hard to get the dye to adhere evenly to the wool.