 Low-level laser light therapy, LLLT, has been studied since 1967, but its use remains controversial due to incomplete understanding of the underlying mechanisms and the selection of inappropriate dosimetric parameters. Studies have shown that LLLT can produce biphasic dose-response curves, meaning that there are two distinct thresholds of effectiveness. These thresholds correspond to different levels of ATP production and mitochondrial membrane potential, which are both important mediators of cellular function. Additionally, some studies have found evidence of a third threshold corresponding to increased oxidative stress. Understanding these biphasic dose-response curves could help optimize clinical treatments by providing more precise dosage guidelines. This article was authored by Ying Ying Huang, Soba Kei Sharma, James Carroll, and others.