THE TAKEAWAY: Evening domestic lighting isn't just a mood choice; high-kelvin overhead LEDs suppress natural melatonin onset.

Specialized intrinsically photosensitive retinal ganglion cells (ipRGCs) in the lower retina detect blue-green wavelengths present in overhead sunlight. Exposure to high-intensity, high-kelvin indoor lighting after sunset signals your brain's master clock (the suprachiasmatic nucleus) that it is midday, delaying sleep architecture. Switching to low-placed, warm (<2700K) lighting in the evening preserves your body's natural wind-down signals.