Book excerpt: This book provides expert coverage of the current state of the art in the application of nanotechnologies to cellulose research. It offers a comprehensive collection of topics including nanocellulose isolation, assembly into hierarchical structures, and advanced emerging applications. During the past decades, research in nanocellulose has advanced quickly, driven by the urgent needs for sustainability and the availability of advanced nanotechniques. Although cellulose has been investigated and used for thousands of years, the recent advances in nanotechnology have transformed our view of this natural substance. Cellulose, when present in the highly crystalline nanoscale form, can demonstrate interesting mechanical, optical, and fluidic properties that can be manipulated in designing materials with novel applications. This book contains 12 chapters. Chapter 1 focuses primarily on the fundamentals of nanocellulose, including general aspects on its structure, isolation, and characterization. Chapters 2-4 summarize the recent progress on assembly of nanocellulose into the macroscopic scale using state-of-the-art techniques. Chapters 5-13 cover the most advanced applications of nanocellulose in emerging areas, including superstrong materials, light management, electronics, energy storage, printed battery, water treatment, nanogenerator, and biomedicine. The book will appeal to upper undergraduate and graduate students through practicing researchers as a comprehensive reference on the subject of nanocellulose and its use in various fields.