**4. Conclusion**

The aim of this chapter was to provide an overview of cellulose nanocrystals and their production by various hydrolysis procedure.

Traditionally extracted from multiple cellulose sources via sulfuric acid hydrolysis, these cellulosic nanomaterials are pioneering for a wide range of applications, briefly introduced in this chapter. Such hydrolysis process has allowed the industrialization of this cellulose nanocrystals since 2011. However, in current context, the development of green chemistry is crucial in this research field, and new alternative process are expected.

In order to support this sustainable strategy, the use of natural deep eutectic solvents for the production of cellulose nanocrystals in mild condition has been very recently developed with interesting and encouraging results.
