 Cellulose nanocrystals, CNC, have unique characteristics that make them widely applicable in diverse fields as a liquid crystal forming material due to their light weight, special optical properties, non-toxicity and biocompatibility. The left-handed cholesteric phase structure of CNC-based LC has corresponding unique optical properties, and the preparation of CNC is discussed. The three stages of forming LC phase in a CNC-based aqueous suspension are also described. However, pristine CNC-based LC can be brittle and non-uniform due to several reasons, which can be overcome through various methods. Optical applications of CNC-based LC films in anti-counterfitting, colorimetric sensors, and composite devices are considered. This article was authored by Xiaoyao Wei, Tao Lin, Min Duan, and others.