Red light at 633 nanometers has a long enough wavelength to penetrate the epidermis (outermost layer of the skin) and reach the dermis (the middle layer of the skin). This enables it to reach fibroblasts, special types of cells that sit beneath the skin and manufacture collagen – a protein that helps tighten and firm the skin and heal wounds.

Red light does this by acting on the mitochondria inside fibroblasts. Mitochondria are small organelles that exist inside most of the cells in your body. They produce the cell’s energy by absorbing oxygen and other materials, as well as by producing a molecule called ATP.

Exposing the mitochondria to red light at 633nm causes a number of changes in mitochondria, particularly, it increases the mitochondrial membrane potential, allowing the mitochondria to receive signals faster. Red light also causes an increase in the production of ATP.

Mitochondria produce ATP by a process called the “electron transport chain.” One enzyme involved in that process is ‘cytochrome c oxidase.’ Cytochrome c oxidase is also a “chromophore”; i.e, a moledule that responds to the presence of light.

Since cytochrome c oxidase is a necessary part in making cellular energy, and since it is stimulated by the presence of red light at 633nm, it will respond by increasing the production of cellular energy. This increases the activity of the cells themselves, and therefore causes the fibroblasts in the skin to produce more collagen to firm, tighten, and improve the overall appearance of the treated area.