The widespread spread of skin diseases requires the most accurate diagnosis at the earliest possible stage, since severe skin diseases can significantly reduce the quality of life of patients and their families and promote the development of psychosomatic diseases. Visual assessment of disease symptoms and severity is often subjective.

From a histological point of view, the skin consists of two layers: the epidermis and dermis, which are closely connected. On a histological cross-section of the skin, the line between the epidermis and dermis appears uneven due to the presence of many dermal papillae separated by the protuberances of the epidermis. The epidermis consists of several layers: the basal layer, the spinous layer, the granular layer, and the stratum corneum. In the epidermis of the palms and feet, there is an additional layer between the granular layer and the stratum corneum - the stratum lucidum. Sometimes, the collection of the basal layer, the spinous layer, and the granular layer is called the malpighian layer.

The dermis is the connective base of the skin, where sweat and sebaceous glands, blood and lymphatic vessels, nerves, and smooth muscles are located. The dermis has a papillary layer and a reticular layer. The papillary layer is located below the epidermis, and part of the reticular layer conditionally forms the upper dermis; the dermis at the level of the pilosebaceous unit is called the middle dermis; the lower layer contains sweat glands and borders the subcutaneous fat, called the deep dermis.

The skin vessels form two anatomical plexuses: a deep layer, located next to the subcutaneous fat, and a superficial layer, located below the papillary layer. They consist of microcirculatory blood vessels: arterioles, venules and capillaries.

The total thickness of the skin without subcutaneous fat varies from a few millimeters to 4 millimeters.

Existing NLS diagnostic systems are equipped with high-frequency linear generators (1.4 GHz) that allow visualization of the structures of the most superficial layers, especially the skin. However, sometimes such frequencies are not enough to assess the condition of the ultra-fine structures of the skin. That is why dermatologists began to use special equipment with sensors operating at a frequency of 40 GHz, which can visualize the finest structures of the skin layers, down to the level of large carbohydrate molecules and peptides. But at the same time, due to the high cost of such equipment, most clinics cannot afford widespread application. Considering the need to evaluate regional lymph nodes and soft tissue tumors, it was clear that the best decision was to use a nonlinear diagnostic device equipped with a nonlinear sensor operating at 4.9 GHz.

The Biophilia Tracker X5 ULTRA system has an axial resolution of 30 µm. This application allows the study of the epidermis at the cellular and subcellular levels.