Adjective
submicrometer (not comparable)
Having a scale less than a micrometer.
An argument that increased jaggedness in the contact line enhances droplet mobility has also been proposed. citation Many hydrophobic materials found in nature rely on Cassie's law and are biphasic on the submicrometer level with one component air. Source: Internet
Composition The particles in tobacco smoke are liquid aerosol droplets (~ 20% water), with a mass median aerodynamic diameter (MMAD) that is submicrometer (and thus, fairly "lung-respirable" by humans). Source: Internet