Polymers are ubiquitous in modern materials science, playing a critical role in a diverse array of applications, from everyday household items to advanced engineering solutions. However, with the growing demand for performance, durability, and cost-effectiveness, the incorporation of fillers into polymer matrices has become increasingly important. Fillers are substances added to polymer formulations to enhance their properties, modify performance, or reduce manufacturing costs. This article explores the nature of fillers, their types, and their impact on polymer properties.