Photobiomodulation is a developing biomedical practice in which a low-level/intensity/power laser or monochromatic light is utilized to modulate biological functions without irreversible damage. It has been widely used to reduce pain and inflammation, accelerate wound healing and hair growth, prevent cell death and tissue damage, and improve blood circulation since the invention of lasers in the 1960s.

Photobiomodulation remains controversial in mainstream medicine. Despite many laboratory experiments and clinical trials, the cellular and molecular mechanisms of photobiomodulation continue to be elusive. A main reason is that the initial physiological state of the treatment object is critical for the treatment response. For example, as Karu (1998) has pointed out, there are no effects of low-power laser irradiation on the cell whose redox potential is so that the cell normally functions. In addition, recent studies have shown there has been the complexity of choosing from a large number of illumination parameters, such as wavelength and treatment dosage (power density and irradiation time). Many negative reports are confusing because they do not include the dose response or pay attention to the initial state. Even positive results contain conflicting data. Thus, future studies need to be carried out carefully regarding these factors.

In spite of these misleading and confusing publications, new and exciting findings are just beginning. In this special issue, we invite authors to present original research articles, as well as review articles, that study the mechanisms of photobiomodulation and its applications. Potential topics include, but are not limited to:

• Homeostasis and photobiomodulation
• Mitochondria and photobiomodulation
• Signal transduction and photobiomodulation
• Low-intensity laser irradiation or monochromatic light
• Moderate intensity laser irradiation or monochromatic light
• Therapeutic photobiomodulation
• Wound healing
• Laser acupuncture

Before submission authors should carefully read over the journal's Author Guidelines, which are located at http://www.hindawi.com/journals/ijp/guidelines/. Prospective authors should submit an electronic copy of their complete manuscript through the journal Manuscript Tracking System at http://mts.hindawi.com/ according to the following timetable: