The scientific explanation for why we dream involves complex brain activity during sleep, particularly during REM (Rapid Eye Movement) sleep. Dreams are thought to originate from activation of brain areas such as the sensory cortex, limbic system, and higher cognitive modules, which synthesize memories, emotions, and sensory signals into vivid experiences. Dreams may serve several functions according to different scientific theories:

• Memory consolidation: Dreams are part of the process by which the brain stabilizes and integrates newly acquired memories into long-term storage. During dreaming, the brain reorganizes and links related memories, which might appear as bizarre dream scenarios.
• Neural activation: Dreaming arises from brainstem activation and internal brain signals during sleep, with decreased activity in parts of the prefrontal cortex that normally suppress impulses, allowing freer, imaginative thinking.
• Emotional processing: Dreaming may help process emotions by activating emotional brain centers such as the amygdala.
• Creativity and problem-solving: Some theories propose dreams foster creative thinking by loosening associative networks in the brain.
• Psychological interpretations: Earlier theories saw dreams as fulfilling unconscious wishes or revealing symbolic meaning.
• Neurocognitive views: Dreams reflect brain simulations based on memory and knowledge without external inputs.

Although dreaming is closely linked with REM sleep physiology, it can also occur in other sleep stages, and the precise biological function remains partly unknown. Dreams may also contribute to cognitive functions like learning or maintaining mental health, but some consider dreaming a byproduct of brain activity without specific function. In summary, dreaming is a complex neurophysiological phenomenon involving brain activation, memory processing, and emotional and cognitive functions during sleep, particularly REM sleep, but its full biological purpose remains an active area of research.