Low reactive level laser therapy (LLLT) and photobiomodulation are mainly focused on the activation of intracellular or extracellular photoabsorbable molecule (chromophore) and the initiation of cellular signaling using low power lasers and lights. Over the past 40 decades, a number of basic and clinical researches were reported that the laser therapy had the potential to improve wound healing and reduce pain and inflammation. In recent years, the term "LLLT" has become widely recognized. In this review, the mechanisms of action of LLLT at a cellular level are described. Finally, our recent research results that LLLT enhanced the cells differentiation are also described.