In this chapter, synthesis techniques of FNMS including bottom-up and top-down approaches were thoroughly described. Bottom-up methods includes co-precipitation, sol-gel, solvothermal, spray pyrolysis, and hydrothermal. Synthesis of various FNMS using this method with their crystal structure, morphology, and size were briefly discussed. The co-precipitation method is a straightforward and cost-effective approach, but the sol–gel and solvothermal procedures provide better crystallinity and uniformity. The synthesis of extremely crystalline ferrites with perfect compositional control is made possible through the use of spray pyrolysis and hydrothermal processing methods. On the other hand, top-down approaches include laser ablation, ball milling, sputtering and thermal evaporation. The influence of synthesis condition on size and morphology of FNMs were explained. Overall, this chapter provides the controlled synthesis of FNMs with their advantages and disadvantages.