It is important to distinguish between wood's natural coloring and variations caused by external factors. Each species has its own grain, and thus its own typical coloring. In the same block of wood, color varies according to the density of the fibers. This is what creates wood's unique pattern. Various natural factors can alter wood's coloring, such as exposure to light, air, and humidity. The color can be changed with stains and varnishes. The effect will vary in intensity depending on the density of the fibers and the degree to which they absorb the stains and varnish.