For a living being, light means more than just seeing: it is energy and information. Plants and humans have both evolved special molecules — called chromophores — that capture certain colors and convert them into energy or biological signals. The molecule differs. The principle is identical.

And the story begins in a surprising place: in a garden grown by NASA, in space. The same research that taught plants to grow under LEDs later led to red light therapy for humans.

The plant "sees" only red and blue

Chlorophyll most strongly absorbs red light (~660 nm) and blue light (~450 nm), but reflects green. That's why leaves are green — that color is, in fact, the light the plant rejects. Red and blue are the engine of photosynthesis and, for this reason, are the basis of LED grow lights.

Red builds. Blue disciplines.

The two colors play complementary roles in the life of the plant:

Combined, red and blue give the characteristic light of horticultural LED systems — the spectrum that plants use most efficiently.

Chlorophyll for the plant, cytochrome for man — the same grammar of light, in two kingdoms.

NASA grew plants in space — and discovered something else

To feed astronauts on long missions, NASA pioneered growing plants under red and blue LEDs. Radishes grown this way developed more chlorophyll, more antioxidants, and more stored energy.

But the real surprise came from elsewhere: researchers observed that wounds on their own skin healed faster under the same red LEDs. That was the moment when light for plants became light for people — and red light therapy was born.

Your body has its own light pigment

Just as the plant has chlorophyll, the body has cytochrome c oxidase — an enzyme in the mitochondria that functions as a light receptor. It absorbs red light (600–750 nm) and near-infrared light (750–1100 nm), precisely the wavelengths in the "optical window" that penetrate deepest into the tissue.

Mitochondria feed on light

When cytochrome c oxidase absorbs these photons, the electron transport chain accelerates: the mitochondria produce more ATP — the energy currency of the cell — modulate reactive oxygen species, and release nitric oxide, which relaxes blood vessels.

Basically, it's a gentle form of "cellular photosynthesis." This is also the principle behind red light therapy — the red light therapy used on the skin to support cellular energy, soothing, and recovery.

And blue? In humans, it speaks to the clock

Blue light has another role in humans: through special cells in the retina, it regulates the circadian rhythm — the internal clock that controls sleep. In addition, it has an antibacterial effect, used against acne.

Precisely why context matters: the same blue light that keeps your mind awake during the day can disrupt your sleep at night, and in excess can stress the skin. In photobiology, wavelength and dose are everything.