Large amounts of waste crab shells are generated at seafood processing plants. The main component, chitin, can be mechanically processed into nanofibers [1]. It can be obtained as a uniform aqueous suspension, which offers superior processability compared to traditional chitin powder (Fig. 141.1). Partially deacetylated chitin nanofibers possess a positively charged surface due to amino groups and can be individually dispersed in water, thanks to electrostatic repulsion [2]. These nanofibers, similar to cellulose, consist of microcrystals and exhibit excellent mechanical properties [3]. They also demonstrate various physiological functions, with effects on the skin (wound healing [4], alleviation of dermatitis, hair growth [5]), ingestion effects (alleviation of intestinal inflammation, dieting, lowering of cholesterol in the blood, intestinal regulation, prevention of fatty liver disease), and plant effects (induction of disease resistance, growth promotion) that have been reported.