Book excerpt: Luminescence, or “cold light,” is observed in everyday life through various forms such as television displays, lighting, mobile devices, and more. Although luminescence has been known since ancient civilizations and documented historically, nowadays it encompasses several types with distinct characteristics and applications. The applications of luminescence continue to expand and play a crucial role in many modern technological advances, making it an appealing field for ongoing development and innovation. This book provides a comprehensive overview of luminescence, discussing the theory, production, and real-life applications of luminescence and luminescent materials.