2D material in three dimensions

The carbon material graphene has no well-defined
thickness; it merely consists of one single layer of atoms. It is
therefore often referred to as a “two-dimensional material.” Trying
to make a three-dimensional structure out of it may sound
contradictory at first, but it is an important goal: if the
properties of the graphene layer are to be exploited best, then as
much active surface area as possible must be integrated within a
limited volume.