Dreams are successions of images, ideas, and sensations that occur involuntarily during sleep. Lucid dreaming involves becoming consciously aware that one is dreaming and taking control of the dream. Some techniques to induce lucid dreaming include dream recall, reality testing, and mnemonic induction of lucid dreaming. Benefits include overcoming nightmares, while risks include sleep problems and derealization. Lucid dreaming has been studied scientifically and has historical and cultural significance in many societies.