Nausea during sleep warns of the arrival of great danger, so you must be alert to any worrying signs.
Gallery of dreams
Some people can recognize dreams while sleeping; this type of dream is called lucid dreaming. Most of the people would have experienced this type of dream atleast once in their life. You can actually control these dreams. One of the popular dreams that most of us experience is as flying in the sky; you can try lucid dream by imagining your house beside the flying aid.
Do animals dream?
Research conducted by various scientists show that animals do experience dream while sleeping. They also experience similar sleep stages like human beings - REM and Non-REM. If you have noticed a dog sleep, it might sometimes wag its tail, this indicates some response to its dream. A study was conducted in a cat by removing a part of the brain stem, which will not prevent it from reacting to the dream during REM. It was noted in some cats they were aggressively chasing mice as in reality.