Objects that have all dimensions below 1um are considered nanoparticles. I say all dimensions, because it is possible to have fibers which are very thin but long. Their volume could be equivalent to that of a nano-sphere, but one of their dimensions can be much above one micron.
Examples of nanoparticles
- Man made nanoparticles can be of different materials. Notably gold nanoparticles can be found in tainted glass . The oldest example I know is the Lycurgus Cup . Also other metal nanoparticles are used for sunscreen since they can be made to absorb UV light.
- Natural nanoparticles can be Extracellular Vesicle s and Virus .