There has been tremendous progress lately in the field of III-nitride (GaN, AlN, InN) semiconductors and their device applications. For example, the invention of III-nitride-based blue laser diodes was the key to a new high-density data storage technology, the Blue-ray disc. Concurrently, improvements in III-nitride-based solid state light sources have led to their use in an increasing number of illumination applications, moving steadily toward the goal of general lighting. This book focuses on three emerging areas for III-nitride applications - chemical and biological sensing, energy conversion and controlled light-matter interactions - and was based on the potential for these applications to improve our quality of life, as well as the superior material properties III-nitrides offer in terms of high chemical stability, excellent biocompatibility, efficient light absorption from the complete solar spectrum and strong light-matter coupling. Topics include: chemical and biological sensing; surface and interface properties; electronic devices; energy conversion; controlled light-matter interactions; light-emitting diodes and growth and processing.