In this collection, the authors begin by presenting recent progress and preparation of cellulose nanocrystals. Additionally, different applications of cellulose nanocrystals as polymeric scaffold material, reinforcement fillers, rheology modifiers, and in electronics are reviewed and discussed. Also provided are detailed descriptions on: cellulose nanocrystals isolation methods, characterization, and properties; current and future trends in terms of development of cellulose nanocrystals for various applications; concluding remarks on cellulose nanocrystals major uses in advanced engineering applications. In view of the rising interdisciplinary research being carried out on cellulose nanocrystals, the authors assemble the knowledge available about the chemical structure, sources, physical and chemical procedures for the isolation of cellulose nanocrystals. In closing, this book gives a brief, up-to-date introductory review on cellulose nanocrystals synthesis, up research in polymer-based cellulose nanocrystals nanocomposites, and their applications and challenges.