The Science of Light & Wellness
Every claim on this website is grounded in peer-reviewed research. Here is the complete scientific framework behind circadian lighting and why it matters for your health.
The Retinal Clock: How Your Eyes Tell Your Brain What Time It Is
Intrinsically Photosensitive Retinal Ganglion Cells (ipRGCs)
Discovered in 2002 by Satchin Panda and colleagues, ipRGCs are a distinct class of retinal neurons that contain the photopigment melanopsin. Unlike rods and cones (which are responsible for vision), ipRGCs are dedicated to non-visual light sensing. They are maximally sensitive to short-wavelength blue light at approximately 480nm — the wavelength most abundant in morning daylight and in modern LED and fluorescent lighting.
The Suprachiasmatic Nucleus (SCN)
ipRGC signals travel via the retinohypothalamic tract to the suprachiasmatic nucleus (SCN) — a paired structure in the hypothalamus containing approximately 20,000 neurons that function as the brain's master clock. The SCN synchronises all peripheral clocks throughout the body, governing the timing of hormone release, metabolism, immune function, and gene expression. The 2017 Nobel Prize in Physiology or Medicine was awarded to Hall, Rosbash, and Young for elucidating the molecular mechanisms of this clock.
The 24-Hour Hormonal Programme
Hover or tap any point on the chart for detailed hormone state and recommended light temperature.
Ideal Light Temperature
The Evidence for Human-Centric Lighting
Scientific Reports (2019)
DOI: 10.1038/s41598-018-36791-5
Blue-enriched morning light (6500K) produced significantly greater cortisol release and melatonin suppression compared to 3500K in university students. Participants reported higher alertness, better mood, and improved cognitive performance.
ScienceDirect (2025)
DOI: 10.1016/j.buildenv.2025.10844
A long-term evidence-based study of circadian rhythm-oriented control strategies for office luminous environments found that a circadian forward lighting pattern produced a 1.5× increase in melatonin secretion compared to static lighting conditions.
Lighting Research Center, Rensselaer Polytechnic Institute
Workers under circadian-supportive lighting showed approximately 50% fewer attention lapses and faster reaction times compared to those under standard static office lighting.
WELL Building Standard v2.1
The WELL Building Standard includes a dedicated Circadian Lighting Design credit, requiring tunable white systems capable of delivering at least 275 equivalent melanopic lux at the eye during morning hours and below 50 EML in the evening.
"The biggest influence on our circadian clock is light. Light-sensing cells in the retina control when we sleep, when we wake, and regulate the production of melatonin. By aligning our light environment with the natural solar day, we can restore biological rhythms that drive health, mood, and performance."
Prof. Satchidananda (Satchin) Panda, Ph.D.
Salk Institute for Biological Studies · Author of The Circadian Code