With the synthesis of a single atomic plane of graphite, namely, graphene honeycomb structure, a new perspective for carbon-based electronics is opened. The one-dimensional graphene nanoribbons (GNRs) have different band-gap values depending on their edge shape and width. In this contribution, we report our results showing that repeated heterostructures of GNRs of different widths form multiple quantum-well structures. The widths of the constituent parts as well as the bandgap, and also the magnetic ground state of the superlattices are modulated in direct space. We provide detailed analysis of these structures and show that superlattices with armchair edge shapes can be used as resonant tunneling devices and those with zigzag edge shape have unique features for spintronic applications. We also discuss another route of functionalizing 2D graphene, 1D GNR, and superlattices with 3d-transition metal (TM) atom adsorption.