The development of new chemically based growth techniques has opened the range of possible GaN applications. This paper reviews some of the challenges in the chemically based growth of GaN and related materials. Ammonothermal-based growth, hydride vapor phase epitaxy and metal organic vapor phase epitaxy (MOVPE) are chemically complex systems wherein the underlying mechanisms of growth are not well understood at present. All these systems require substantial experimental and theoretical efforts to determine the nature and kinetics of GaN growth. In the case of metal organic vapor phase epitaxy, the application of computational techniques based on density functional theory have augmented the more conventional experimental approaches to determining the growth chemistry. These chemical reaction schemes, when combined with computational thermal-fluid models of the reactor environment, provide the opportunity to predict growth rates, uniformity and eve ntually materials properties.