As the world population is increasing at a rate that is much higher than what can be supported with the present potential of crop yield, a sustainable increase in the world food production is required. This requires crop improvement to maximize yield from limited land and other available resources. The alteration of endogenous Gibberellins' levels is an effective tool for improvement of many agronomic traits in crops. This book deals with the description of modification of GA metabolic and signaling pathway for crop improvement by various approaches. The evolution of components involved in GA biosynthesis and response pathways in fungi,lower plants,dicots and monocots is also described which indicates that the approach can be applied to different crop plants. The constraints in GA level modulation are also highlighted with reference to existing homeostasis mechanisms in plants, its cross-talk with other hormones, and its regulation by the complex hormonal web which affect GA levels. This strategy possess the potential of further revolutionizing the agriculture once the complete mechanism of the regulation of plant growth and development by integrated hormonal network becomes clear.