micropore
noun
mi·cro·pore ˈmī-krə-ˌpȯr 
: a very fine pore
microporosity
ˌmī-krə-pə-ˈrä-sə-tē
noun -pȯ-
microporous
ˌmī-krə-ˈpȯr-əs
adjective 
Example Sentences
Recent Examples on the Web In a similar vein, the ceiling is lined with Majilite Nytek vinyl, a porous material that breathes by transmitting moisture vapor through billions of tiny micropores. 
Megan Barber, Curbed, 6 Apr. 2018 As expected, the acid dissolved the calcite, leaving nothing but a weakened black sponge full of micropores. Laura G. Shields, Science | AAAS, 12 Dec. 2017
Megan Barber, Curbed, 6 Apr. 2018 As expected, the acid dissolved the calcite, leaving nothing but a weakened black sponge full of micropores. Laura G. Shields, Science | AAAS, 12 Dec. 2017 Word History
Etymology
International Scientific Vocabulary
First Known Use
1884, in the meaning defined above