Dreams, most experts believe, are messages from our subconscious. Buried feelings and fears are called up and interwoven with events that take place during the day. But in sleep, these messages are often disguised-and that's what makes dreams so fascinating. Scientists say there's no chance about it: everybody dreams! Even people who say they never dream actually do-they just don't remember their dreams. How do scientists know? They have watched people dream in sleep laboratories. At a sleep laboratory, volunteers are hooked up to electronic monitoring equipment. An electroencephalograph, or EEG, records brain waves-the electrical impulses that are constantly given off by the brain. Other machines monitor eye movements and heart and breathing rates. The volunteers' job is easy-they simply go to sleep. But all night long, scientists keep watch on the monitoring equipment. Brain waves vary with the brain's activity, so watching the EEG tells scientists what's going on while the volunteer is sleeping. Heart rate and other physical signs also vary through the night. (Grolier Book of Knowledge Encyclopedia)