The escalating demand for sustainable alternatives to fossil-based resources has intensified global interest in biomass-derived bio-based materials. This chapter explores the fundamental concepts, classifications, and advancements in bio-based materials originating from biomass, emphasizing their pivotal role in fostering green innovation. It begins with a comprehensive overview of biomass and its transformation into diverse bio-based materials, distinguishing between energy-based and material-based applications. The biomass main components in terms of cellulose, hemicellulose, and lignin are discussed for their structural characteristics and relevance to material synthesis. The chapter further examines agricultural waste and by-products as promising feedstocks, detailing their categorization, valorization pathways, and potential for industrial applications. A particular focus is given to the evolution from micro- to nano-scale bio-based materials, highlighting the significance of bio-nanocomposites and nano-biosensors in sectors such as packaging and food safety. Additionally, state-of-the-art analytical techniques for characterizing mechanical, thermal, and chemical properties are discussed to support material optimization. Overall, this chapter underscores the transformative potential of bio-based materials from biomass in achieving environmental sustainability, resource efficiency, and technological innovation across multiple industries.