Nightmares are vivid, frightening and disturbing dreams that occur during the rapid eye movement (REM) stage of sleep. They often involve feelings of fear, anxiety, terror or stress and can cause the dreamer to wake up feeling unsettled or distressed. Nightmares are a common experience for many people and can be triggered by a variety of factors such as stress, trauma, anxiety, medication or sleep disorders. Research in this area focuses on understanding the causes and effects of nightmares, as well as developing effective treatments and interventions to help individuals cope with and reduce the frequency of nightmares. Techniques such as imagery rehearsal therapy, cognitive behavioral therapy and medication may be used to help individuals manage and overcome recurrent nightmares.