This chapter explores the application of trichomorphology for taxonomical purposes. Throughout the book, the focus is on guard hairs, which are the most universally used and diagnostically significant type of hairs in taxonomy—i.e. they possess the most comprehensive diagnostic criteria. Once hairs are sampled, they must be meticulously prepared for microscopic examination. Detailed descriptions are provided for the physical and chemical methods required to prepare hairs for effective examination of the medulla and cuticle. These methods include the preparation of microscope slides, techniques for preparing and using gelatin to obtain clear cuticle imprints, the application of specific types of turpentine to clarify the medulla, and, in extreme cases of completely darkened medullas, the use of peroxide to discolour hairs. This chapter concludes with a discussion on the various morphological criteria to be examined once the preparation of the microscope slides is completed.