The standard trichogram provides information about the number of Anagen hairs and Telogen hairs from different parts of the scalp. While this information is accurate and quantitative, it only reveals part of the story. It tell us how many hair fibers are growing, but it takes no account of those hair follicles that may not contain any hair fibers at all. It does not tell us about the density of the hair on the scalp and hair density (scalp coverage) is the primary concern for any individual experiencing hair loss. In response to this deficiency, the standard trichogram can be taken several steps further and developed into a variation of the trichogram called the "unit area trichogram". In the unit area trichogram procedure the plucked hairs are taken from an area of skin that is measured. So, for example, a circle a centimeter in diameter my be marked on the skin and then all the hairs in that circle will be plucked out and examined. In this way the number of Anagen, Catagen and Telogen hair counted can be used to define the density of these hair types per unit area of scalp. This density measurement gives an idea of how thick or thin the hair coverage over the scalp skin is. The Trichologist can say you have certain amount of Anagen, Catagen and Telogen hair per square centimeter of the scalp. Knowing what the normal hair fiber density is for the average person from published studies (ranges from 200 to 300 hair fibers per square centimeter depending on ethnicity), your evaluation may be presented in terms of how close your hair density is to the normal expected value. If the measurement is repeated over time the Trichologist can say whether the hair coverage is getting thicker or thinner. This method quantifies the cosmetic appearance of scalp hair growth. It can be used to see how well a hair loss treatment is performing and how much new hair the treatment has induced to grow. As well as looking at the frequency and density of the hair fiber types, the diameters of the hair fibers may be measured under the microscope. Normal terminal hairs should have a diameter of 80 micrometers of above for most people. Between 40 micrometers and 80 micrometers diameter the hair fibers are usually defined as "intermediate hairs". These hairs are not healthy, but they are thick enough to contribute to the overall coverage of the scalp skin. Below 40 micrometers diameter the hair fibers are certainly not healthy and they do not help much to cover the scalp. These fine hairs are usually well on their way to becoming Vellus hairs, if they have not already reached that state. So by taking the additional step of measuring the plucked hairs diameters, the Trichologist can determine the density of healthy hairs, or the density of those hairs that can contribute to hair coverage.