Nanofillers are small particles, ranging from 1 to 100 nm, composed of metals, metal oxides, polymers, and ceramics. They possess unique properties compared to their larger counterparts, making them versatile in various fields like medicine, electronics, energy, and environmental science. Nanofillers can be engineered with specific characteristics like high surface area, reactivity, and optical or magnetic properties. Their small size allows them to interact with biological (e.g., cells and tissues at a molecular level) and non-biological entities, opening up possibilities for various applications (e.g., drug delivery and diagnostics). However, nanoparticles’ impact on health and the environment requires careful research and regulation. This condensed chapter provides an overview of nanofillers, including their types, applications, and advancements. It categorizes nanofillers into carbon-based and non-carbon-based nanoparticles, establishing a foundation for researchers and engineers. The chapter emphasizes the significance of nanofillers in materials science and their potential for future developments. It also summarizes key advancements in nanofiller research and addresses future directions and challenges. Overall, the chapter highlights the unique properties and applications of nanofillers while acknowledging the need for responsible investigation and management of their effects.