Light as a Forest of Colors

Imagine walking in a dense forest at noon. Sunlight pours down from above, but not all colors of light reach the forest floor. Blue and green light are mostly absorbed or scattered by the leaves, barely touching the plants below. Red and orange light, however, filter through the canopy, reaching the forest understory and nourishing the plants there.

In your body, the situation is similar. The “canopy” is made of skin, fat, and other tissues. Red and NIR light act like the filtered sunlight that can penetrate this canopy, reaching the “understory” — the mitochondria within your cells — without causing any harm.