As Example 1, I describe the development of a generalized MOVPE crystal growth model based on elementary processes and its application to the high-accuracy prediction and control of the composition and thickness of nitride alloys. Nitride semiconductors have been widely used in practical applications such as blue LEDs, solid-state lighting, and high-frequency wireless devices, and metalorganic vapor-phase epitaxy (MOVPE) is widely employed for the growth of high-quality crystalline layers. However, MOVPE involves complex interactions among precursor decomposition, gas-phase transport, surface incorporation, crystallization, and desorption. Because changes in growth parameters such as temperature, pressure, and gas flow rates strongly affect crystal quality, composition, and layer thickness, reproducing target values requires extensive experimentation and considerable time.　Conventional models are based on detailed reaction processes and are therefore not well suited for general-purpose applications because of their high computational cost and the difficulty of parameter identification. In this study, we developed a generalized growth model that considers only simple elementary processes, namely, the incorporation efficiency of source materials and the desorption rates of constituent materials. Using this model, we demonstrated that the alloy composition and layer thickness during growth can be predicted and controlled with high accuracy solely from the gas-phase supply ratios of the source materials. These results enable simple yet highly accurate control of composition and layer thickness during crystal growth, which is essential for the fabrication of nitride semiconductor heterostructure devices.