The currently used strategies for the nanoparticles’ synthesis are top-down and bottom-up.

Synthetizing nanoparticles by top-down strategies means to start from bulks and miling it, using several approach, to reach nano size. Conversely, the production of nano object starting from atoms or building blocks is called bottom-up strategy.

For example, metal nanoparticles dispersed in solution are usually synthetised starting from metal salt precursor mineralized in present of reducing agents.