Lucid dreams are dreams we have control over because we are aware we are dreaming. With this type of dream, people usually decide what to dream about before they fall asleep and dream of that very thing when they are sleeping.
Psychologists used to think that it was impossible to be conscious during sleep, but research has shown that lucid dreams are real and seem to be triggered by high levels of stress, anxiety and physical or mental activity during the day.
Some people claim they can encourage themselves to have lucid dreams by simply thinking about their state of consciousness while they're awake or by waking up in the middle of the night and doing something active before going back to sleep.