Particles below 50 nm in diameter (0.05 μm).
ultra-fine dispersed, solid particles (in the size range of colloids), possessing a high specific surface to volume ratio, the properties of nanoparticles are mainly determined by the surface; the preparation and the properties of nanoparticles are investigated by the nanotechnology science and the colloid chemistry
Clusters of a few hundred or thousand atoms that display very different properties (often useful) from bulk aggregates of trillions. They are created with standard aerosol or solution chemistry techniques -- i.e. with no precise control of atom count or placement.
Particles ranging from 1 to 100 nanometers in diameter. Semiconductor nanoparticles up to 20 nanometers in diameter are often called quantum dots, nanocrystals, or Q-particles.
A nanoparticle is a microscopic particle whose size is measured in nanometers (nm). It is defined as a particle with at least one dimension less than 200nm. http://en.wikipedia.org/wiki/Nanoparticles
Sometimes referred to in 'cosmetics' advertising, as a 'breakthrough' that makes products even better. These are VERY small particles, less than 100 billionth of meter in size. They are extremely easily absorbed by the skin, they can easily pass across the blood/brain barrier – their potential to cause harm is unknown and largely un-investigated... Another innovation marketed as a wonderful feature to get you to 'BUY', which could yet prove to make some syntheticchemical based products even more dangerous