A dream can warn us of potential danger, and decoding our dreams can often help us to solve problems. Frequently, things that trouble us crystallize in a dream. Some dreams even predict the future. Studying and interpreting dreams isn't new, as they have fascinated man since the dawn of time.
Dreams have been carved on cave walls, set in stone, and every Roman Legion had a soothsayer to try and make sense of 'nocturnal visions'. In ancient times, priests consulted oracles and shrines for guidance, to try and make sense of dreams.

Our ancestors believed that dreams were messages from the gods, and in days gone by, interpreters of dreams were visited much as doctors are today. Times may have changed, but the fascination of dreams remains. Many now-famous people have put forward theories of dream interpretation.

Sigmund Freud thought that much of what we dream is in some way sexual. Another psychoanalyzer, Carl Jung, recognized that man has other deep desires to drive him. In his fascinating book, An Experiment with Time, Professor Dunne put forward the idea that all time is like a river, and that it can be navigated backwards or forwards in the vessel of dreams. Sleep is the road to dreamland. And these days, thanks to advances in medical science, we certainly know more about it than our predecessors did.

On average, we sleep for a third of each day; by the time we're 75, we have slept for 25 years - and dreamt for 10 of them. That's a lot of sleeping, and a lot of dreaming! Recent studies show that what occurs in dreams takes place in a real-life time-span, so, for instance, simple things like shopping or eating take just as long in a dream as they do in reality.

In more complicated dreams, however, where you're, say, in far-flung places, you're simply seeing the 'edited highlights'. Studies also have shown that it's possible to dream with your eyes open, which happens when the brain becomes overloaded with the toxins created by fatigue.

In extreme exhaustion, the person will succumb to the need for sleep - but the dream will be cut short by an inbuilt desire to survive, for example, if they have started dreaming at the wheel. It's long been accepted that the ideal position for a good night's sleep is to be on the right-hand side of the bed. The bed should be facing north-south, so that the body can make maximum use of the lines of magnetism running from the Poles. Try running your hands in cold water before retiring as well - it can get rid of surplus static.

If you find it hard to sleep, try breathing very deeply in through your nose and out through your mouth. This is a very helpful technique for becoming calm. When we fall asleep each night, a complex series of changes in our consciousness takes place.

Deepest sleep comes upon us almost immediately. This is followed by a shorter period of lighter sleep in which our eyeballs dart about beneath our closed lids. This period of Rapid Eye Movement - or REM - is when we dream. It happens about five times in an eight-hour period. We usually wake up after the last one, and naturally these are the dreams we remember best.

There is some evidence that women dream for longer periods than men. Perhaps they simply enjoy their dreams more! Any kind of drugs - whether stimulants or sedatives - diminish the amount of dream time. So if you're ill or taking medication, you're less likely to dream. Dreams that you have while ill can be discounted as you're reacting to the illness rather than to a normal course of events.

Some people claim they never dream, but this is simply because they don't remember their dreams as well as others. Clinical tests have proved that when so-called non-dreamers are woken during REM sleep, they give vivid accounts of the images they have just seen, which are, like real-life events, in colour. Even our pets dream. If you watch a sleeping dog or cat, you can detect their Rapid Eye Movement.

Many people claim they can't remember the content of a dream on waking. Because dreams are an expression of our true selves - including desires we can't admit even to ourselves, let alone others - dreaming is the only way we have of expressing them. We sometimes find it hard to accept the messages that are being given in a dream, and so we censor them.

Dreams are heavily loaded with emotion, and this can distort our memory. To help remember your dreams, try keeping a dream diary. On waking, don't get out of bed or even change position. Keep a notepad and pen by the bed, or even a tape recorder, and note down or record everything you can remember. Try and recall, too, what you were preoccupied with before going to sleep as this can provide vital clues in interpretation. Try to recapture the mood of the dream, which is important. If you still can't remember, but an event later in the day triggers your memory, write it down. It could be helpful in working out the meaning of the dream. Train yourself to do this regularly, and gradually memories of your dreams should follow.

Dreams are a proven creative artistic source: some of our greatest writers and poets, like Robert Louis Stevenson and William Wordsworth, regularly recorded their dreams and were inspired by them. In dreamland, many wonderful things can happen: we can travel to distant places, meet loved ones, even take tea with the Queen. Some dreams, however, can simply be scary, and a particularly frightening dream is called a nightmare.

These severe anxiety dreams - where you wake up in a cold sweat, feeling very afraid - occur because what is happening in the dream is too overwhelming to be contained while asleep, so you wake up. True nightmares occur in the non- dream phase of sleep, and have little remembered content.

Sex plays a major part in our dream world. That's because it has an important role in our everyday lives. It's a powerful driving force, like hunger and ambition. While we're awake, sex is ruled by social restrictions and conventions, but in our dreams, even the most timid of us can have explicit and excitingly sexy dreams once our repressed selves are asleep. That's why the prissiest of spinsters often uses filthy language when waking from an anesthetic. Sex is a significant bodily need, and any unusual or enforced period without it might result in a sexual dream. Frank sexual dreams can occur frequently in adolescence, and often result in actual orgasm. In adults, everyday sexual needs and preoccupations are dealt with indirectly in dreams.