In the quiet hours we surrender to sleep, science is discovering that darkness itself may be a form of medicine. Recent research has found that even low levels of light during sleep — from screens, lamps, or the ambient glow of modern life — are associated with measurable changes in the heart's structure and function, quietly accumulating cardiovascular risk over time. The bedroom, long treated as a passive refuge, is emerging as an active environment that shapes our health in ways previous generations never had to consider. As with diet and exercise, what surrounds us in our most vulnerable h