Caffeine works primarily by blocking the action of a chemical called adenosine, which slows down our neural activity, allowing us to relax, rest, and sleep.

Melatonin is a hormone that regulates sleep-wake cycles.

It's based on the idea that by partitioning your sleep into segments, you can get away with less of it.

Especially before bed. Phones and tablets emit light that’s skewed heavily toward the blue end of the visible spectrum and these frequencies are especially influential in human sleep cycles.