It is a scientific consensus that dreams are products of the unconscious. But what is the unconscious? By definition, it is neither accessible to an empirical nor a phenomenological description. This work aims to deduce the necessary and probable influencing factors from a detailed and comprehensive phenomenological analysis of the dream phenomenon using a scientifically precise and executed method (the so-called reductive-regressive analysis), without which the dream could not appear in its phenomenality. Through this approach, it becomes possible to determine the inner nature of the unconscious in a relaxed manner and thus for the first time to scientifically verify the origin of dreams and the essence of the underlying unconscious.