What did dimitri iwanowski do?

Answer 1

I believe you may be referring to the Russian Botanist Dmitri Ivanowski (1864-1920)

Along with a colleague he discovered that a certain disease in tobacco plants is caused by a pathogen that can pass through filters too small for bacteria to pass through.*

He did this by grinding up infected tobacco leaves and after passing them through tiny ceramic filters then applied the ground and filtered substance to other leaves of healthy tobacco plants which were infected. The significant part of his experimentation was that he showed bacteria could not possibly have caused the disease and something smaller than bacteria must exist which can cause disease. We now know these are viruses.

*parts paraphrased from: Robert Bauman's "Microbiology" pg 15, Pearson, Toronto, 2009.

Answer 2

a Russian Scientist