Nanoparticles are not visible
![212_air_particule_1](/images/stories/Ressources/2-METROLOGIE/212_air_particule_1.jpg)
Industrial pollution.
![212_air_particules_2](/images/stories/Ressources/2-METROLOGIE/212_air_particules_2.jpg)
Urban pollution.
Nanoparticles (< 100 nm) are not visible without instrumentation. So we must imagine them from photos of particles of a few tenth of mm (for example, in situations of pollution).