Light, sleep and your body clock.

The best light for sleep is bright and blue-rich by morning, then warm, dim and blue-free by evening. Here is what the science says, and how to set up your lighting.

Blue light in the evening is the strongest signal telling your body clock it is still daytime. Here is how to reduce it, and why screen filters alone are not enough.

To reset your body clock, anchor it with light: bright light right after you wake, dim and blue-free light before bed, and a consistent wake time. Shift gradually.

Light, especially blue-cyan light in the evening, can delay and suppress melatonin, the hormone that signals night to your body. Darkness lets it rise on schedule.

The best night light for sleep is a very dim, warm or amber/red one. Cool white and blue night lights carry the most of the signal that keeps the body clock awake.

Bright light soon after waking is the most effective way to feel alert and set your body clock earlier. Here is how much, how long, and what to do on dark mornings.

Bright, cool, blue-rich light during the day supports alertness, focus and mood. Dim indoor lighting is part of why the afternoon slump hits. Here is how to fix it.

Shorter winter days mean less morning light, which can leave your body clock drifting and your energy flat. Bright light in the morning is the most useful fix.

The fastest way to beat jet lag is to shift your body clock with light at the right times. Here is the simple rule for eastward vs westward travel, and how to pre-adjust.

Night shifts fight your body clock. You cannot fully flip it, but the right light during and after your shift, plus darkness for day sleep, makes a real difference.

Circadian or human-centric lighting is designed to support your body clock, not just vision: bright and blue-rich by day, warm and blue-free by night. Here is how it is measured.

Most smart bulbs change what you see, not the signal your body clock reads. Here is what actually matters in a circadian bulb, and how the types compare.