Currently, nano-biotechnology and engineered nanomaterials are the key imperatives in the spotlight. Atoms make up everything on Earth, including the food we eat, the clothes we wear, the houses we live in, and our bodies which are all atoms. Research is still on them due to their increased performance over their bulk equivalents and their customizable physical, chemical, and biological properties. Engineers and scientists are developing numerous methods to produce materials at the nanoscale, to benefit from their enhanced features, including higher light spectrum control and chemical reactivity compared to their macroscale counterparts. Since there are various applications of nanoparticles in different fields, including cosmetics, tissue engineering, dental filling resins, and food packaging, strenuous efforts should be exerted in this scientific discipline to produce nanoparticles, nanocomposites, and nanofillers that have proven their efficiency resulting in today’s massive growth in material sciences. New technologies are continually developed to fulfill the growing demand for various developed applications depending on nanotechnology. Nanofillers are added as a cement enforcement material to give new superior characteristics to polymers and nanocomposites to enhance their properties and also their performance, including physical, mechanical, and resistance, allowing them to be used in many fields in the polymer market like electronics, sensors, and others exploiting their novel properties. Thus, it is vital to understand their properties, types, and synthesis methods to improve them, increase their efficiency, and innovate new ways for synthesis at low costs with higher yields. This chapter provides a detailed overview of the different synthesis methods of nanofillers, their different physical and chemical properties, and some applications, adding to the main types of nanofillers that will be covered.