Trichoscopy allows analyzing the structure and size of growing hair shafts in their natural environment in children and adults. The method replaces light microscopy, which requires pulling of multiple hairs for investigation. In monilethrix, trichoscopy shows uniform elliptical nodosities with intermittent constrictions. In trichorrhexis nodosa nodular thickenings along hairs shafts are visible (low magnification) or splitting into numerous small fibers along the hair shaft may be observed (high magnification). In trichorrhexis invaginata (bamboo hair) the hair shaft telescopes into itself at several points along the shaft. Trichoscopy shows small nodules along the shaft. Hairs bend and break in these diseases. Trichoscopy of pili torti shows twists of hair shafts along their long axis. In pili annulati hair shafts with alternating white and dark bands are visible. In woolly hair the examination demonstrates hair shafts with waves at very short intervals. For trichothiodystrophy polarized trichoscopy should be used. In ectodermal dysplasias, trichoscopy shows a variety of hair abnormalities, but the most characteristic finding is hair shaft pigmentation heterogeneity.