The role of daytime residues in dream formation is variable. Sometimes they are indifferent and serve as substitutes for the dream wish. Sometimes they are the main instigators of the dream and find paths of elaboration in dream regression. These two paths of dream formation are in line with the distinction proposed by Freud between dreams from below and dreams from above. The author returns to the multiple questions raised by this distinction and the way in which Freud approaches the relations between dream life and waking psychic functioning. This distinction also opens out onto the study of the other dream functions, namely the binding and regulation of the psychic economy. The dream work presides over the meshing of perceptual activity with drive activity thanks to the operation of distortion and thus contributes to the construction of chains of thought. If dreaming is essential to our psychic health, it is also essential to our physical health, as the psychosomaticians of the Paris School have shown.