## 5 Conclusions  
In this review, the structure and properties of all cellulose nanomaterials were first shown; then, the three types of nanocellulose--crystalline, fibrous, and bacterial--their synthesis processes, their peculiarities, and, finally, their characterization techniques, were summarized. Moreover, these nanomaterials have also demonstrated to be good substitutes for synthetic products in the field of the conservation and recovery of cultural heritage, where they can be used for several applications. Here, the most recent developments, results, and findings about nanocellulose-based consolidants were presented, with particular attention on the recovery and reinforcement of degraded wood and stabilization of painting canvases and historical papers. In the case of wooden artifacts, one of the most important results obtained is the possibility of reducing the use of non-renewable petroleum sources and enhancing the use of eco-friendly wood adhesives, reached with the easy functionalization of nanocellulose. In addition, for waterlogged wood, nanocellulose-based consolidants have also achieved excellent results in terms of consolidation and interactions with the structure of wood, comparable to those obtained with synthetic consolidants. For the painting canvases, nanocellulose is gradually taking the place of synthetic resins usually used as consolidant, thus providing better results both in terms of mechanical properties and stability toward moisture changes, also sometimes allowing for a very innovative approach that simultaneously provides a consolidating and deacidifying action without affecting the visual appearance of the artwork thanks to the addition of nanoparticles of calcium carbonate or magnesium oxide. Finally, regarding the degradation of paper, the primary medium for recording information throughout the world, all nanocellulose types are better solutions due to their compatibility with paper and eco-friendliness. The use of Japanese paper, which, despite its good results, creates considerable thickness and does not reach the legibility of the characters after processing obtained with nanocellulose-based treatments, can be overcome. Moreover, with the addition of specific metal nanoparticles in the nanocellulose suspensions, it is also possible to reach antibacterial activity, thus hindering degradation due to the formation of mold and bacteria attacks, or also an UV light protection. The future challenge of these research works concerns the study of the variability of nanocellulose properties, which are influenced by the type of nanocellulose, the manufacturing processes, and the natural sources from which it is extracted. However, the study of large-scale nanocellulose production processes will definitely need to be deepened in order to make it an easily available and low-cost material, obviously taking into account the \"green\" aspect and therefore the bio-compatibility and eco-sustainability of the synthetic procedures, coping with the dictates of the EU Green Deal. All of these improvements will allow us to use these nanomaterials and their composites in different fields of applications, including that of cultural heritage, where the use of cellulose nanomaterials would avoid synthetic consolidating agents harmful to both artworks and the health of operators working in the field of fine arts. This will only be possible with an interdisciplinary research work that aims toward the study and improvement of nanocellulose materials with a low environmental impact and high technological content for increasingly advanced and sustainable applications in order to benefit from the knowledge preserved in the cellulose artworks for as long as possible. **Author Contributions:** The manuscript was written through contributions of all authors. All authors have read and agreed to the published version of the manuscript. **Funding:** This work was supported by Regione Lazio (FOR FSE Lazio 2014-2020). **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable.