The work presents the first developments of the application of the active imagination techniquein Jung's life, its emergence, as well as how to use it when he recommended it to some of his patients and, later, to other analysts, and seeks to show the differences between active imagination and other similar approaches, such as: fantasy directed, passive fantasy, creative fantasy. The fundamental question, however, is: What makes active imagination such a peculiar instrument that it makes it a dialogue with the unconscious? It is certainly one of the most intriguing themes proposed by Jung and, although it has been elaborated throughout his life, only recently, through The Red Book (2010), it became accessible, leaving, as an inheritance, the mandatory task of knowledge and dissemination of this material. The Red Bookit reports on the active imaginations recorded by Jung, as he lived them, with the most authentic psychic material of himself. Naturally, everyone who is willing to take an individual path must “dig” and find his own. Such a purpose requires goodwill, willingness, energy, time, dedication, courage, humility, or the imposition made by the unconscious itself, through dreams, visions, symptoms and fantasies. In parallel with the technique of active imagination, the research addresses another fundamental concept of Jung, which is the transcendent function , since both are directly associated.