Nanotechnology is very ancient technology and its usage was first recorded in the 9th century. There are many cases of ancient objects utilizing nanocomposites; impressive examples are glass that alters color due to reflection of light and steel swords with incredible strength, crushing resistance, and extraordinarily sharp edges. Nanoparticles have a wide surface area and many particles per unit mass compared with microparticles. Initially, observations of nanoscale particles were gold-related. There are different synthetic methods for nanoparticle synthesis such as bottom-up, hydro/solvothermal, and top-down. The bottom-up methods include organic ligand-assisted growth, mediated synthesis of small molecules and ions, 2D template-confined growth, and seeded growth. The hydro methods include crystal phase transformation, biological synthesis, and nanoparticle assembly. The top-down methods include the mechanical compression method, exfoliation, and nanolithography. © 2021 Elsevier Inc. All rights reserved.