Sleephaslongbeenregardedasnothingmorethanawaytochargeourbatteries.Butwhatifitcancontrolourweight,allowustomakememories,andhelpustofightoffdiseaseslikeAlzheimer’s?Wetraveltheworldtoinvestigatehowrevolutionarynewtechnologyhasrevealedthesleepingbrainasanenergeticandpurposefulmachine.