Sleep lighting refers to the quality, color, and intensity of light in the environment during the hours before and during sleep. Light is one of the most powerful environmental signals influencing the body’s internal clock (circadian rhythm) and the production of melatonin, the hormone that promotes sleepiness. Getting sleep lighting right is therefore a crucial element of good sleep hygiene. Exposure to bright, blue-spectrum light — such as that emitted by LED bulbs, computer screens, smartphones, and tablets — in the evening suppresses melatonin production and delays the onset of sleepiness. This is because the blue wavelengths of light closely mimic daylight, signaling to the brain that it is still daytime. Reducing exposure to blue light in the two hours before bed can significantly improve sleep onset and quality. Practical strategies for optimizing sleep lighting include dimming overhead lights in the evening and using warm, amber-toned bulbs (2700K or lower). Night mode or blue light filters on screens can reduce blue light emission, and blue-light-blocking glasses are another option. Blackout curtains or an eye mask can help maintain darkness throughout the night, which is important for sustaining melatonin levels during sleep. In the morning, exposure to bright natural light helps to suppress melatonin, boost alertness, and reinforce the body’s circadian rhythm. Opening curtains or going outside shortly after waking is a simple and effective habit. By thoughtfully managing sleep lighting throughout the evening and night, it is possible to support the body’s natural sleep-wake cycle and improve both the ease of falling asleep and the quality of sleep achieved.