Formation of the sheath and presheath in edge plasmas of magnetic confinement fusion devices is briefly discussed.One important aspect of a plasma flowing to the wall that must be included in the analysis is the presheath mechanism provided by the Lorentz force in a magnetic field oblique to the wall or in a spatially varying magnetic field.Another aspect is existence of energetic electrons which has dramatic effects both on potential formation and on heat transport through self-consistent separation of two electron species and induction of secondary electron emission.