Cellulose is the most abundant natural polymer, found in plant fibers. It can be processed into nanosized fillers like cellulose nanocrystals (CNC) and microfibrillated cellulose (MFC), which are used to enhance the mechanical and barrier properties of biocomposites. These nanofillers are being explored for industrial applications, particularly in packaging. The paper reviews the preparation, properties, and applications of cellulose-based nanocomposites, highlighting their potential for sustainable and efficient systems. Natural fibers, primarily plant-based, consist of cellulose, lignin, and hemicellulose. Cellulose microfibrils are the basic structural components, formed during biosynthesis. Cellulose exists in different crystalline forms, such as cellulose I and II, with varying properties. CNCs are obtained through acid hydrolysis, while MFCs are produced by mechanical disintegration. Both have unique properties, with MFCs being long, flexible, and having a web-like structure. Cellulose whiskers, derived from CNCs, are highly rigid and have a high Young's modulus. They are used as reinforcing agents in nanocomposites. MFCs, on the other hand, are used in various applications due to their high surface area and flexibility. The preparation of these nanofillers involves processes like acid hydrolysis, mechanical shearing, and enzymatic treatment. Nanocomposites are materials containing nanosized fillers, such as cellulose whiskers or MFCs, dispersed in a polymer matrix. These composites offer improved mechanical properties and are being explored for applications in packaging, textiles, and other industries. The paper discusses the challenges in dispersing cellulose nanofillers in non-polar media and the use of surfactants and chemical modifications to enhance their compatibility with polymer matrices. The review also highlights the importance of understanding the unique properties of cellulose nanofillers and their potential in developing sustainable and high-performance materials. The use of cellulose-based nanocomposites is seen as a promising alternative to traditional materials, offering environmental benefits and improved performance. The paper emphasizes the need for further research to optimize the production and application of these materials.Cellulose is the most abundant natural polymer, found in plant fibers. It can be processed into nanosized fillers like cellulose nanocrystals (CNC) and microfibrillated cellulose (MFC), which are used to enhance the mechanical and barrier properties of biocomposites. These nanofillers are being explored for industrial applications, particularly in packaging. The paper reviews the preparation, properties, and applications of cellulose-based nanocomposites, highlighting their potential for sustainable and efficient systems. Natural fibers, primarily plant-based, consist of cellulose, lignin, and hemicellulose. Cellulose microfibrils are the basic structural components, formed during biosynthesis. Cellulose exists in different crystalline forms, such as cellulose I and II, with varying properties. CNCs are obtained through acid hydrolysis, while MFCs are produced by mechanical disintegration. Both have unique properties, with MFCs being long, flexible, and having a web-like structure. Cellulose whiskers, derived from CNCs, are highly rigid and have a high Young's modulus. They are used as reinforcing agents in nanocomposites. MFCs, on the other hand, are used in various applications due to their high surface area and flexibility. The preparation of these nanofillers involves processes like acid hydrolysis, mechanical shearing, and enzymatic treatment. Nanocomposites are materials containing nanosized fillers, such as cellulose whiskers or MFCs, dispersed in a polymer matrix. These composites offer improved mechanical properties and are being explored for applications in packaging, textiles, and other industries. The paper discusses the challenges in dispersing cellulose nanofillers in non-polar media and the use of surfactants and chemical modifications to enhance their compatibility with polymer matrices. The review also highlights the importance of understanding the unique properties of cellulose nanofillers and their potential in developing sustainable and high-performance materials. The use of cellulose-based nanocomposites is seen as a promising alternative to traditional materials, offering environmental benefits and improved performance. The paper emphasizes the need for further research to optimize the production and application of these materials.