**5. Summary and Outlook**

During the last decade, significant advances have been made in the preparation, characterization and application of CNC/GNM hybrids. This article is a brief review of this fast-growing research area and intended to highlight the up-to-date studies and utilization of CNC/GNM hybrids. Firstly, we have introduced some basic concepts of nanocellulose and GNM, then summarized their preparation methods and properties, with a particular focus on their outstanding features to elucidate their unique attributes. The different preparation processes of CNC/GNM have been discussed as well as their properties. Furthermore, to well understand the characteristics of theses hybrids, their different applications have been provided.

CNC/GNM hybrid-based materials displayed interesting innovative features due to synergetic effects, which are unachievable by taking CNC and GNM materials separately. It is shown that the combination of the diversity and specificity of both CNC and GNM not only expands the number of applications but also has indisputable advantages to benefit their unique attributes. These hybrids hold a cornucopia of favorable properties that warrant their employment in the fields of sensing, catalysis, separation, electronics, optics, biomedical, energy storage, to name a few. Nonetheless, the development of CNC/GNM hybrid-based materials is relatively a new concept, which is mostly limited to academic discipline but is expected that CNC/GNM hybrids will certainly be commercially available in the future, which will attract more research attention not only in various applications but also to achieve multifunctional multi-systems and open new perspectives. Moreover, the practical application of such hybrids as next-generation materials requires further improvements in functionality and performance in addition to the reduction of the production costs and the environmental impacts. **Author Contributions:** Conceptualization, D.T.; Methodology, D.T.; Investigation, D.T.; Resources, D.T.; Writing original draft preparation, D.T., V.K.T. and R.B.; Writing-review and editing, D.T., V.K.T. and R.B.; Supervision, D.T., V.K.T. and R.B. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was financially supported by the Ecole Militaire Polytechnique.

**Conflicts of Interest:** The authors declare no conflict of interest.
