The size-dependent properties of nanomaterials are fundamental to their unique behavior and applications across various scientific and technological fields. As materials are reduced to the nanoscale, they exhibit properties that differ significantly from their bulk counterparts, including changes in electrical, optical, magnetic, and mechanical characteristics. These alterations arise primarily due to the quantum effects, surface-to-volume ratio, and increased surface energy at the nanoscale. For instance, nanoparticles can exhibit size-dependent electronic bandgap variations, which impact their optical absorption and photoluminescence properties, making them ideal for light-emitting devices and solar cells. Similarly, the magnetic properties of nanoparticles, such as superparamagnetism, are influenced by size, leading to applications in data storage and biomedical imaging. The mechanical strength of nanomaterials, which is often higher than bulk materials due to their defect-free structure, has made them promising candidates for use in lightweight composites and high-strength materials. Additionally, the chemical reactivity of nanomaterials is enhanced by their high surface area, making them effective in applications like catalysis and environmental remediation. Understanding these size-dependent behaviors is crucial for designing and optimizing nanomaterials for specific applications in energy, electronics, healthcare, and beyond.