Trichoscopy is a recently suggested new method of hair and scalp evaluation and is used for diagnosing hair and scalp diseases. The method is based on Dermatoscopy and Videodermatoscopy. The method has been concurrently developed in various European Trichological/Dermatological groups in Poland, Italy and United Kingdom starting from 2004. The term “trichoscopy” was first suggested in 2006 by Polish Trichologist Lidia Rudnicka and coworkers. In trichoscopy hair and scalp structures may be visualized at many-fold magnification. This method allows viewing of the hair and scalp at X10 to X1000 magnifications. Trichologic structures which may be visualized and distinguished by trichoscopy include hair shafts of different types: Terminal; Vellus (or Vellus-like), which by definition are 0.04 mm or less in thickness; micro-exclamation mark type which may be 1 to 2 mm or less in length; structural hair shaft abnormalities may be visualized, such as monilethrix, pili annulati hair, etc; the number of hairs in one pilosebaceous or follicular unit may be assessed. It may be distinguished whether hair follicles are normal, empty, fibrotic ("white dots"), filled with hyperkeratotic plugs ("yellow dots") or containing cadaverized hair ("black dots"). Abnormalities of scalp color/structure which may be visualized by trichoscopy include honeycomb-type hyperpigmentation, perifollicular discoloration (hyperpigmentation) predominant in Alopecia Androgenetica, and perifollicular fibrosis, characteristic for some forms of Fibrosing Alopecia, cutaneous microvasculature often may be seen in scalps. Additionally scaling intensity may be evaluated, most Trichologists use a 5-point intensity scale (0 = no scaling and 4 = severe scaling). Specifically in Alopecia Androgenetica trichoscopy allows visualization of abnormalities which are known from researches performed with invasive and semi-invasive techniques. One of most characteristic features of inherited hair loss is heterogeneity of hair shaft diameters. The diversity in hair diameter is the main and most accurate clinical parameter linked to follicle miniaturization and trichoscopy allows to perform precise measurement and monitoring of hair shaft thickness in Alopecia Androgenetica. Accordingly, identifying and counting Vellus hairs (thin hairs of less than 0.04 mm in width) is possible. Without the need to perform multiple scalp biopsies the Terminal to Vellus hair ratio may be calculated. Via trichoscopy, Alopecia Androgenetica has been characterized by an increased percentage of thin hairs, decreased average hair diameter, predominance of hair follicle units with single hairs, presence of hyperkeratotic plugs (yellow dots), and perifollicular hyperpigmentation. Characteristic images of specifically female Alopecia Androgenetica include hair shaft heterogeneity and increased percentage of thin (below 40 micrometers) hairs at the vertex. Alopecia Areata is characterized by regularly distributed yellow dots, black dots, micro-exclamation mark hairs, dystrophic, and regrowing hairs. Trichoscopy allows also distinguishing Alopecia Cicatricica from noncicatricial type of hair loss. Also trichoscopy proved usefull in diagnosing children with congenital hair shaft abnormalities. Trichoscopy requires special equipment called a videodermatoscope or trichoscope with usual working magnifications from X10 to X1000. It is beneficial to be equipped with special software, which enables measurement of visualized structures and conversion of measurement results into a data sheet. Some hair abnormalities may be seen with a handheld dermatoscope, but this device is not sufficient for precise hair evaluation in many diseases. A regular trichoscopy screening should include evaluation of hair and scalp in the frontal, occipital, and parietal areas. In selected cases other locations are chosen for trichoscopy; these may include the scalp in various locations as well as eyebrows and eyelashes. The choice of immersion fluid is needed in case of large magnifications being used. It is a matter of individual preference, as aqueous, gel, alcoholic, and oily immersion fluids in regard to image clarity and tendency to form air inclusions (bubbles) may be used. Lately it also serves as a research tool in evaluation of disease severity and for monitoring treatment efficiency in various acquired hair and scalp diseases associated with hair loss. For example, trichoscopy was used to monitor the impact of dutasteride therapy on hair thickness and hair shaft heterogenity in Alopecia Androgenetica. It has been shown that the method may be used as a research tool to evaluate the effect of different therapeutic agents or cosmetic products on hair and scalp condition. Trichoscopy clearly shows the effect of different therapeutic treatments, it has a great advantage of being noninvasive and allowing precise measurement of visualized structures, thus it is gaining popularity as an accessory tool in differential diagnosis of hair loss. This makes trichoscopy a valuable research tool, especially in frequent and long-term monitoring.