The article discusses the mechanisms, applications, and current state of low-level laser (light) therapy (LLLT), also known as photobiomodulation. It outlines the historical development of LLLT, starting from the 1960s with the invention of the ruby and helium-neon lasers, and its subsequent evolution into a widely used therapeutic modality. LLLT involves exposing cells or tissues to low-intensity red and near-infrared (NIR) light, which is distinct from higher-intensity lasers used for cutting or coagulation. The therapy is characterized by a biphasic dose response, where both low and high doses can be beneficial, but there is an optimal range for therapeutic effects. The article reviews the cellular and tissue mechanisms of LLLT, focusing on its effects on mitochondria, ATP production, reactive oxygen species (ROS), and transcription factors. It also discusses the interaction of light with biological tissues, including absorption, reflection, and scattering, and how these processes influence the penetration and distribution of light within tissues. The article highlights the use of various light sources, including lasers and light-emitting diodes (LEDs), and the importance of proper dosimetry in achieving effective therapeutic outcomes. LLLT is applied in a wide range of clinical settings, including wound healing, pain relief, inflammation reduction, and the treatment of neurological conditions. The article summarizes the results of numerous clinical trials, noting that while some studies show promising results, others are inconclusive due to variability in parameters such as wavelength, fluence, and power density. The article also discusses the potential of LLLT in treating serious conditions such as stroke, spinal cord injury, and traumatic brain injury, as well as its use in hair regrowth and intravascular therapy. Despite its growing acceptance, LLLT remains a topic of debate due to the lack of a comprehensive understanding of its biochemical mechanisms and the variability in treatment outcomes. The article emphasizes the need for further research to establish standardized protocols and to clarify the optimal parameters for different applications. Overall, the article provides a comprehensive overview of the current state of LLLT, its mechanisms, and its potential in various therapeutic contexts.The article discusses the mechanisms, applications, and current state of low-level laser (light) therapy (LLLT), also known as photobiomodulation. It outlines the historical development of LLLT, starting from the 1960s with the invention of the ruby and helium-neon lasers, and its subsequent evolution into a widely used therapeutic modality. LLLT involves exposing cells or tissues to low-intensity red and near-infrared (NIR) light, which is distinct from higher-intensity lasers used for cutting or coagulation. The therapy is characterized by a biphasic dose response, where both low and high doses can be beneficial, but there is an optimal range for therapeutic effects. The article reviews the cellular and tissue mechanisms of LLLT, focusing on its effects on mitochondria, ATP production, reactive oxygen species (ROS), and transcription factors. It also discusses the interaction of light with biological tissues, including absorption, reflection, and scattering, and how these processes influence the penetration and distribution of light within tissues. The article highlights the use of various light sources, including lasers and light-emitting diodes (LEDs), and the importance of proper dosimetry in achieving effective therapeutic outcomes. LLLT is applied in a wide range of clinical settings, including wound healing, pain relief, inflammation reduction, and the treatment of neurological conditions. The article summarizes the results of numerous clinical trials, noting that while some studies show promising results, others are inconclusive due to variability in parameters such as wavelength, fluence, and power density. The article also discusses the potential of LLLT in treating serious conditions such as stroke, spinal cord injury, and traumatic brain injury, as well as its use in hair regrowth and intravascular therapy. Despite its growing acceptance, LLLT remains a topic of debate due to the lack of a comprehensive understanding of its biochemical mechanisms and the variability in treatment outcomes. The article emphasizes the need for further research to establish standardized protocols and to clarify the optimal parameters for different applications. Overall, the article provides a comprehensive overview of the current state of LLLT, its mechanisms, and its potential in various therapeutic contexts.