Sleeping on it - how REM sleep boosts creative problem-solving

The German chemist Friedrich Kekule claimed to have intuited the chemical structure of the benzene ring after falling asleep in his chair and dreaming of an ouroboros (a serpent biting its own tail). He's certainly not the only person to have discovered a flash insight after waking from a good sleep. In science alone, many breakthroughs were apparently borne of a decent snooze, including Mendeleyev's creation of the Periodic Table and Loewi's experiments on the transmission of nervous signals through chemical messengers.