Sleep is not oblivion but an active aperture onto the hidden workings of the mind, thus only ever as empty as a stage awaiting creation. Dreaming REM sleep is the space of memory's reconsolidation and vital sorting out of the overwhelming detail of lived life, but also of inspiration and of those endless strange realignments of the components of waking life we remember in snatches. For all that we understand of the essential nature of dreaming, the images created by the sleeping mind retain some ineffable mystery. And what lies in those other unsleeping unconscious states, those of a coma or true blackout? And what, also, does a fossil dream across the millennia?