Thymus species are aromaticAromatic perennialPerennial herbaceous plants or subshrubs belonging to the Lamiaceae family. HealthHealth benefits and aromaticAromatic properties of thymeThyme known from the ancient era, however, the spectrum of various industrial and domestic utilization areas expanded considerably. Several thymeThyme species applied as resources of dried drugs, spices, essential oilsEssential oil, extracts and oleoresinsOleoresin. Almost all of the therapeutic effects of the extracts and essential oilsEssential oil applied internally are in connection with the respiratory system, since it is a good expectorant having antispasmodicAntispasmodic and antiseptic effects as well. According to the literature reported on factors influencing composition and biological activityBiological activities of thymeThyme essential oilEssential oil, we can conclude that genetic features, environmental conditions, growing as well as processing technologies have all significant effect on the final product and quality parameters. Concerning genetic background, the presence of different chemotypesChemotype with distinct chief compounds in the essential oilEssential oil influence principally the areas of utilization. The main constituent of commercial thymeThyme oil is predominantly thymolThymol with the highest therapeutical relevance attributed to Thymus species. Therefore, breedingBreeding efforts made in order to develop varieties with high essential oilEssential oil content as well as elevated thymolThymol percentage. In this chapter, we present an overview of the origin, distribution, taxonomic position, genetic diversityGenetic diversity and conservationConservation, cultivationCultivation practices and recent developments on biotechnologyBiotechnology and molecular biology with their application for crop improvement in association with conventional breedingBreeding methods of thymeThyme.