Various techniques have been used to grow III-nitride heterostructures including metalorganic vapor deposition, hydride vapor epitaxy and molecular beam epitaxy (MBE). Among these techniques, MBE presents a number of advantages such as precise control of layer thickness and composition. MBE is a highly sophisticated system which thin film quality is sensitive to the growth parameters. From the literature, a systematic growth procedure has not been well-documented. This book presents an in depth understanding of MBE growth mechanism which is essential for thin film quality improvement. Detailed study on the growth mechanism allows the acquisition of the fundamental knowledge in growing precise optoelectronics device structures. This book focuses on the study of III-nitride thin films grown by MBE on various aspects, supported by analysis using a variety of structural and optical characterization techniques. The book starts with the introduction of the MBE architecture, follows by the detailed growth procedures. The characterization and analysis of various III-nitride thin films grown on Si and sapphire will be presented in the last part of the book.