What causes you to dream within a dream?

Although the idea of having a "dream within a dream" has become very popular because of the movie Inception, that material is Science Fiction. There is nothing that "causes" a dream within a dream. If such claims are made by individuals, books or websites, one should be very suspicious of fraud.

On the other hand, the subconscious mind can produce a dream that involves falling asleep and dreaming. In such cases, the "dream within the dream" is a symbol used by the mind to tell the dreamer that in some aspect of real life they need to "wake up" and stop "dreaming." In other Words, the meaning of a dream within a dream is that the dreamer needs to think more realistically.