The biodegradability of nanocellulose (NC) promotes its use as an eco-precursor for several purposes. The extraction of this nanomaterial from undesirable wastes, besides achieving green disposal of these wastes, will boost the eco-friendly nature of the products. This chapter highlights on the methods of preparing the nature-based NCs, and bacterial-based NCs, techniques of their characterization, as well as how the synthesis route will affect the properties of the nanoproduct, and summarized the strategies to be followed for enhancing their performance in different applications, such as sustaining release of drugs (e.g., medical application), thermal stability for application in HDPE-composites, dispersing/adsorbent of dyes, as well as in electronics and energy purposes. This chapter aims to provide a comprehensive overview of the synthesis methods, structural and physicochemical characterization, and performance enhancement strategies of nanocellulose derived from both natural and bacterial sources. It also seeks to demonstrate the relationship between synthesis methods and final material properties, and to highlight its emerging applications across medical, environmental, and industrial sectors.