Root hairs are cylindrical in shape outgrowths of root epidermis. They are characterized by the tip growth which relies on the deposition of new components of cell membrane and cell wall at the tip of the growing hair. The main role of root hairs is to extend the root surface, uptake of water and mineral soils. They are responsible for building interactions with soil microorganisms, and in some species, they synthesize and secrete bioherbicides. The development of root hairs is a complex process that involves many proteins, enzymes and cellular structures. It can be divided into several phases: formation of rhizodermis pattern, initiation of root hair development by bulge formation, transition to the tip growth and the tip growth itself. Up to date, several dozens of genes involved in root hair formation have been described and about 40 of them were characterized at the molecular level. Among them, there are genes encoding transcription factors, cell wall components and variety of enzymes, including kinases family and GTPases. Many of proteins are involved in cell signaling, cytoskeletal dynamics or vesicular trafficking. Plant hormones, mainly ethylene and auxin play also an important role in root hair development. Although the type of root hair growth is rather distinctive among the plant cells, many biochemical pathways that lead to their development are universal, and because of the relative ease of their observation, root hairs can serve as a good model of plant cell differentiation. The paper presents a comprehensive review on the genetic and molecular control of root hair development in a model plant Arabidopsis thaliana.