Trichomes (also named plant hairs) are tiny epidermal outgrowths with special functions found and covering the aerial surfaces of nearly all plants. They are uni or multicellular, branched, or unbranched structures and can take many shapes and forms. Branched hairs can be dendritic (treelike), tufted, or stellate (star shaped). Trichomes posses a variety of functions: glandular secretor or absorption organs, supporting, and defense mechanisms or protection against insect predators. Glandular trichomes contain volatile oils and other chemicals secretions that are produced, for example, by aromatic plants or culinary herbs. On the contrary, some glandular trichomes break off when are touched, penetrating the skin or mucosal tissue of humans and animals and may inject a poisonous or irritant substance. There are some references in the literature in the presence of trichomes in cytological smears and skin specimens. On the presence of trichomes in cytological smears and histological sections (Figs. 1–4), airborne and/ or waterborne contamination in the staining procedure is the most probably hypotheses. In both techniques, haematoxylin is used, and tap water is used for bluing the preparations, being in this step when most probably may success the contamination. Furthermore, in case of sputum samples, oral contamination must be considered too. Most of trichomes are microscopic, because their resemblance with certain micro-organisms is very important to recognize some morphological features in order to avoid misinterpretations, especially with worms (Strongyloides stercoralis, microfilarias, and other larval nematodes) and hyphae of fungi. Absence of recognizable internal organs, inflexed body, and existence of a wrinkled blunt end (the insertion zone) are important details in order to differentiate trichomes from worms. In case of hyphae, absence of a fungal septa or budding and sharp ending may help in the differentiation. Because trichomes show birefringence, polarized light also is useful to distinguish these structures from these parasitic elements.