Drug nanocrystals belong to a group of modern therapeutic nanosystems seeking to improve pharmaceutical and/or biopharmaceutical properties of biologically active ingredients. Pharmaceutical-technological methods can be divided into two main groups, according to the type of development of drug nanocrystals: (i) top-down methods and (ii) bottom-up methods. The main aim of this diploma thesis was to study scientific literature and abstract the latest information on nanocrystal technology and dermal application of nanocrystals. The efficacy of dermal application depends on the complex interrelationship of the properties of biologically active ingredients, substrates properties and skin properties. The physicochemical properties of biologically active ingredients often limit their application. By using nanocrystal technology, it is possible to provide better efficacy of poorly soluble biologically active ingredients after their dermal application. Due to increased saturation solubility, increased dissolution velocity and, consequently, increased adhesiveness, pharmaceutical form with embedded nanocrystals shows improved dermal bioavailability, compared to the conventional formulations. Further development and application of nanocrystal technology of biologically active ingredients will certainly contribute to more effective and safer treatment of various skin diseases.