Molecular techniques are being increasingly employed in the field of dermatology, significantly enhancing the management of cutaneous disorders. These applications have become important diagnostic tools, not only in the setting of genodermatoses, but also in a wide range of cutaneous malignancies and infectious diseases. In addition, molecular testing has been used to select treatment, assess therapeutic response, and predict prognosis. This chapter provides an overview of the principles and applications of the molecular technologies most frequently used for the diagnosis and study of cutaneous diseases (Table 3.1)