The real world in nono-scale is more like you building something from legobloxks or rubber balls.
You will never have a perfectly 2 dimensional object.
If it where perfectly 2 dimensional (thin), it would simply be transparent for everything, and thus not noticable.
The object in question is comprised of two dimensional particles like Joozey was talking about. The object doesn't have any depth to speak of, so it completely lacks mass. Nevertheless, while it lacks volume, it still has area, so the object could be thought of as a two dimensional plane in 3D space.
