In recent years tremendous efforts have been made to exploit the exceptional properties of 1-Dimensional carbon nanotubes and 2-Dimensional graphene in order to interconnect those forming 3-Dimensional hybrid systems. Such macroscopic 3-D networks possess several advantages such as highly accessible surface area, minimized agglomeration or re-stacking, enhanced thermal and electrical transport, and robust mechanical properties as compared to their nanoscale 1-D or 2-D building blocks. This review aims to provide a fundamental understanding of state-of-the-art synthesis methodologies for interconnecting these carbon nanostructures, structure-property relationships as well as potential environmental applications related to adsorption, catalysis, sensing, and energy conversion. The technical challenges and future research opportunities are also discussed. (C) 2016 Published by Elsevier Ltd.