Red light interacts with the body in a similar way to infrared light – This it thought to involve a few mechanisms including by increasing energy (ATP) generation on the cellular level. The key difference between red and infrared is that red wavelengths of light are absorbed and used in the first 25mm of skin tissue, whereas infrared light can penetrate much deeper into the body. This same mechanism is also responsible for many of the benefits of sunlight, which contains the red wavelengths as part of its spectrum.  Blue light, making red light therapy different in various respects. Most red light devices on the market are weak and will only penetrate 2 – 3mm of skin tissue. Stronger devices such as 100mW/cm²+ LED light devices can reach through the entire skin layer, healing from the bottom up.