BNCs are also known as bacterial cellulose, microbial cellulose, or biocellulose. BNCs are microfibrils concealed by aerobic bacteria, such as acetic acid bacteria of the genus Gluconacetobacter, as a pure component of their biofilms. The resulting microfibrils are microns in length, have a large aspect ratio with morphology de­pending on the specific bacteria and culturing conditions. These bacteria are wide­spread in nature where the fermentation of sugars and plant carbohydrates takes place. In contrast to other forms of cellulose, that is, MFC and NCC, materials isolated from cellulose sources, BNC is formed as a polymer and nano material by biotechnological assembly processes from low-molecular weight carbon sources, such as d-glucose. The bacteria are cultivated in common aqueous nutrient media, and the BNC is excreted as exopolysaccharide at the interface to the air. The result­ing form-stable BNC hydrogel is composed of a nanofiber network (fiber diameter: 20-100 nm) enclosing up to 99% water. This BNC is proved to be very pure cel­lulose with a high weight-average molecular weight (MW), high crystallinity, and good mechanical stability. The bio-fabrication approach opens up the exciting op­tion to produce cellulose by fermentation in the sense of white biotechnology and to control the shape of the formed cellulose bodies as well as the structure of the nanofiber network during biosynthesis. The resulting unique features of BNC lead to new properties, functionalities, and applications of cellulose materials.7078