Delta waves are a type of brain wave that occur during deep sleep. They are characterized by their slow frequency, typically ranging from 0.5 to 4 Hz. These waves are essential for restorative sleep, helping the body and mind recover and rejuvenate. Delta waves are most prominent in the NREM sleep stages, particularly during the deep sleep phase. In addition to their role in sleep, delta waves are also associated with healing and regeneration. They can be measured using an electroencephalogram (EEG), which records electrical activity in the brain. Increased delta wave activity is often linked to improved immune function and overall well-being.