The concept of infantile psychosis has introduced a deep change in the treatment of children suffering of severe developmental disorders. The paper draws a history of the concept including the clinical description of infantile autism by Leo Kanner and of symbiotic psychosis by Margaret Mahler. It shows how from the seminal work of Melanie Klein, Winnicott and Rion, French psychiatry has developed new types of part-time institutions inspired by a psychoanalytical frame of reference. The author describes as an example his own experience in Villeurbanne, near Lyon, and the theory which lays behind this experience. He insists on the narrative of the everyday life and of the interaction between the children and their care providers as an important therapeutic tool.