The Latin words hortus (garden plant) and cultura (culture) together form horticulture, classically defined as the culture or growing of garden plants. Horticulturists work in plant propagation, crop production, plant breeding and genetic engineering, plant biochemistry, plant physiology, and the storage, processing, and transportation of fruits, berries, nuts, vegetables, flowers, trees, shrubs, and turf. They improve crop yield, quality, nutritional value, and resistance to insects, diseases, and environmental stresses. Genetics is also used as a valuable tool in the development of plants that can synthesize chemicals for fighting disease (including cancers).