"A human hair fiber is a thin structure (about 0.1 mm in diameter) with either a circular or oval cross section. The active part, called the follicle, is located under the skin and produces the keratin proteins that compose the hair material. The second part, the visible – and dead – part of hair, is called the hair shaft, and corresponds to the “hair strand”. The hair shaft is entirely synthesized by the asociated follicle, which acts as a mold for shaping the strand. It thus has almost uniform cross section, natural twist and natural curvatures all along. These geometric parameters are associated with commonsense notions of straight, curly, or fuzzy hair. Their values are characteristic of the ethnic group from which the hair comes. Africans have follicles with a helical form and an oval cross section, whereas Asians have follicles that are completely straight with a larger and circular cross section. As a result, Asian hair is thicker, with no natural curliness. It makes it look smooth and regular. In contrast, African hair looks frizzy and irregular. Caucasian hair stands between these two extremes." Source: http://www-evasion.imag.fr/Publications/2006/BACQLL06/sigFinalHair06.pdf