Photobiomodulation (PBM) is a promising new therapy that uses gentle, non-damaging light—like low-level lasers or LEDs—to help the body heal and function better. This chapter takes a closer look at how PBM works, starting with how cells absorb light and how this sparks a chain reaction of biological processes that support healing and repair. The authors delve into how PBM influences key cellular functions, mainly how it boosts energy production in mitochondria, reduces harmful oxidative stress, and even affects how genes behave. The chapter also explores the application of PBM for the regeneration of damaged areas in the brain, muscle and nervous system. The chapter also emphasises the importance of various parameters, such as wavelength, intensity, and duration, in the effectiveness of PBM therapy. In the final sections, the authors also elucidate real-world applications of PBM to manage diabetes, neurological conditions, and inflammatory disorders, and to ease side effects after radiation treatment. Drawing from a wide body of current research, this chapter highlights how PBM is not just a scientific curiosity but a versatile tool with real potential to transform patient care.