Low-level laser therapy (LLLT) uses low-power visible or near-infrared light to promote tissue healing, reduce inflammation, and relieve pain. Despite its long history, LLLT remains controversial in mainstream medicine due to inconsistent results from studies. A biphasic dose response is frequently observed, where low levels of light have a better effect on tissue stimulation and repair than higher levels. This biphasic response is often described by the Arndt-Schulz curve. The review discusses the molecular and cellular mechanisms of LLLT, including the role of mitochondrial respiration, reactive oxygen species (ROS), nitric oxide (NO), and the transcription factor NF-κB. LLLT is thought to work by stimulating cellular processes such as ATP production, increasing cell proliferation, and reducing apoptosis. However, excessive light can lead to harmful effects, including increased ROS and NO, which may inhibit cellular functions. The biphasic dose response suggests that optimal therapeutic effects are achieved at lower light doses, while higher doses may be detrimental. The review highlights the importance of carefully controlling parameters such as wavelength, fluence, and treatment time to achieve the desired therapeutic outcomes. LLLT has shown promise in treating various conditions, including wounds, arthritis, and neurological injuries, but further research is needed to fully understand its mechanisms and optimize its application.Low-level laser therapy (LLLT) uses low-power visible or near-infrared light to promote tissue healing, reduce inflammation, and relieve pain. Despite its long history, LLLT remains controversial in mainstream medicine due to inconsistent results from studies. A biphasic dose response is frequently observed, where low levels of light have a better effect on tissue stimulation and repair than higher levels. This biphasic response is often described by the Arndt-Schulz curve. The review discusses the molecular and cellular mechanisms of LLLT, including the role of mitochondrial respiration, reactive oxygen species (ROS), nitric oxide (NO), and the transcription factor NF-κB. LLLT is thought to work by stimulating cellular processes such as ATP production, increasing cell proliferation, and reducing apoptosis. However, excessive light can lead to harmful effects, including increased ROS and NO, which may inhibit cellular functions. The biphasic dose response suggests that optimal therapeutic effects are achieved at lower light doses, while higher doses may be detrimental. The review highlights the importance of carefully controlling parameters such as wavelength, fluence, and treatment time to achieve the desired therapeutic outcomes. LLLT has shown promise in treating various conditions, including wounds, arthritis, and neurological injuries, but further research is needed to fully understand its mechanisms and optimize its application.