submicron
adjective
sub·mi·cron ˌsəb-ˈmī-ˌkrän 
1
: being less than a micron in a (specified) measurement and especially in diameter
a submicron particle
2
: having or consisting of submicron particles
a submicron metal powder
Example Sentences
Recent Examples on the Web That device gathered information about sperm movement at the level of submicron resolution, smaller than one-millionth of a meter. 
Courtney Sexton, Smithsonian Magazine, 31 July 2020
Courtney Sexton, Smithsonian Magazine, 31 July 2020 Word History
First Known Use
1916, in the meaning defined at sense 1
Medical Definition
submicron
adjective
sub·mi·cron -ˈmī-ˌkrän
1
: being less than a micron in a (specified) measurement and especially in diameter
a submicron particle
2
: having or consisting of submicron particles
submicron aerosols