This paper aims to demonstrate that the Freud/Fliess correspondence was an important apparatus to Freud psychoanalysis invention. The letters reading allows us to follow the emergence of new concepts (phantasy, Oedipus, etc.) and how they required from Freud a subjective journey that culminated in the invention of the psychoanalyst, a place which is different from the relation between a physician and a patient. Hence it follows that this correspondence, that Freud didn't want to publish, has the meaning of the analitical link invention's rest.