Background: The versatility and immense potential of nanoparticles and nanostructures have made them crucial building blocks for a wide range of applications. Achieving precise control over their size, shape, and functionality has become a vital focus in nanotechnology research. Method: This comprehensive review explores the cutting-edge advancements in tailoring the size, shape, and functionality of nanoparticles and nanostructures. It covers a wide array of advanced mechanical, physical, chemical, and biological approaches utilized in their production. The review encompasses an extensive range of synthesis methods, including mechanical milling, high-pressure homogenization, mechanical alloying, mechanochemical synthesis, physical vapor deposition, laser pyrolysis, ion and electron irradiation, laser ablation synthesis, arc discharge synthesis, plasma synthesis, electrospinning, printing, chemical vapor deposition, sol-gel processes, aerosol-based processes, electrochemical deposition, polymerization synthesis, hydrothermal and solvothermal synthesis, microwave-assisted synthesis, ultrasonic synthesis, microbial synthesis, and plant extract-based synthesis. Finding: The ability to control the size, shape, composition, and surface functionalities of nanoparticles and nanostructures is dependent on factors such as raw materials, synthesis methods, and processing parameters. Consequently, the selection of the optimal synthesis method and precise control of reaction conditions and processing parameters are of utmost importance in obtaining nanomaterials with desired properties and achieving targeted applications.