Most people think of light as something they see. Researchers who study photobiology think of it differently: as information — a signal your body has been reading for hundreds of thousands of years.
Two Pathways, One Signal
There are two primary ways light is understood to communicate with human biology.
The Eye Path. Your retina contains specialized cells called intrinsically photosensitive retinal ganglion cells (ipRGCs). Unlike the rods and cones used for vision, these cells contain a photopigment called melanopsin and are believed to send signals directly to the suprachiasmatic nucleus (SCN) — the brain's master clock. This pathway is thought to be central to circadian entrainment, the process by which your internal clock stays synced to day and night.
The Skin Path. Separately, when light contacts skin, different wavelengths appear to trigger distinct processes. UVB radiation (280–315nm) is understood to convert a compound in the skin into vitamin D3. UVA (315–400nm) penetrates more deeply and has been studied in connection with nitric oxide release. Near-infrared wavelengths (700–1100nm) are absorbed by cytochrome c oxidase in the mitochondria, a process researchers are studying as photobiomodulation.
Why Wavelength Matters
Not all light does the same thing. A narrow-spectrum LED bulb and a full-spectrum sunrise both technically produce "light," but they contain very different information.
This is part of why the specific spectrum of a light source is relevant, not just its brightness. A standard indoor LED can measure high in visible lux while still lacking the infrared and ultraviolet components present in natural daylight.
Why This Matters for How You Design Your Light Environment
Understanding these pathways reframes how you might think about your own light exposure. It's not just "get outside more" — it's about which wavelengths you're getting, at what time, and in what dose.
This is the working framework behind Mitolux devices: the BTS2 delivers Red, NIR, and UVB (without UVA), while the Solar X adds UVA to more closely approximate the full solar-noon spectrum. Neither is a substitute for outdoor sunlight, but both are designed around the same photobiological principles researchers are actively studying.
The Bigger Picture
Light science is still an evolving field, and much of the research — particularly around photobiomodulation — is preliminary or based on smaller studies. But the underlying premise, that specific wavelengths carry specific biological information, is well established. Understanding how light works is the first step to understanding why your light environment might matter more than you've been told.