Sleep is essential for resting our minds and bodies, and it's controlled by a mysterious phenomenon known as our internal body clock. This 'master clock' is located in the hypothalamus of our brains, and is established during the first months of our lives. It controls the timing of our nightly sleeps through the release of the chemical melatonin.
While most people's body clock runs roughly to a 24-hour cycle, melatonin release can peak anywhere from 9pm to 3am, depending on the individual. It's this difference in chemical release timing that sees some people become night owls, and other early risers.
Once we're asleep, our brains will cycle through different levels of consciousness, from deep sleep to rapid eye movement sleep (REM). REM sleep is the period throughout which we dream, and it's thought to be a crucial part of memory storage, and works like a recharger for the brain. Most people have four or five dreams every night, but we usually don't remember them.
Find out why people who don't get enough sleep are more likely to overeat, and what the longest recorded period without sleep is by watching the latest episode of RiAus's A Week in Science above.