What do your dreams mean?
Have you ever been about to give a big presentation at work but realise at the last minute you are totally naked? How about being lost in a dark forest and all your teeth have fallen out? In real life, hopefully not. But when you dream you find yourself in all sorts of strange scenarios.
All humans dream - but why? Are dreams just a kaleidoscope of random images or can they tell us something about our waking lives?
For thousands of years people have been fascinated by dreams and have come up with many theories about their function and meaning.
What are dreams?
Dreams are a collection of images and stories that we experience when we sleep. Dreams can entertain us and make us feel happy. They can also be scary and upsetting. Sometimes they are just downright weird.
"At a scientific level, we really know very little about dreams and why we have them. Many 'oneirologists' - posh word for dream scientists - use the term 'sleep mentation' to describe thoughts and imagery that arise from the sleep state," explains consultant neurologist Dr Paul Reading, who has a special interest in sleep science.
"Most would say a dream refers to a sequence of thoughts or images, usually in a narrative or story, often with elements of recent and distant memories in a bizarre or surreal setting. If unpleasant, the word 'nightmare' is used," explains Paul.
Some experts think dreams are just a mish-mash of things that have happened to us in the day. Others believe dreams are a subconscious projection of our hopes and fears. Some think dreams may be able to teach us things about ourselves or even give us insight.
Apparently, Albert Einstein came up with the theory of relativity in a dream. A nightmare of Mary Shelley's inspired her to write Frankenstein and the hit Beatles song 'Yesterday' came to Paul McCartney in a dream.
"Many discoveries and scientific insights have been attributed to dreams but proof is difficult," says Paul.
Some dreams even appear to predict future events. Though experts believe that's most likely down to faulty memory or coincidence.
We don't know 100% for certain what dreams are and why we have them. There are many suggestions. A philosopher and psychiatrist may view dreams differently. A neurologist may have an alternative opinion to a spiritualist.
Why do we dream?
We dream mainly when we are in the phase of sleep known as REM sleep or rapid eye movement sleep.
"We sleep in cycles and it's in REM sleep where you are doing the most emotional and mental processing. REM sleep is where your brain is a powerhouse. If you look at brain waves during REM sleep it looks similar to wakefulness," says Dr Guy Meadows, sleep physiologist and clinical director at the Sleep School.
"Thirty percent of your sleep on average is REM and it doesn't all come in one chunk. Sleep occurs in cycles of one and a half to 2 hours," adds Guy.
People generally have 3 or 4 dreams a night but usually only remember the last one, if at all.