The scientist who studies living organisms too small to be seen with the naked eye is a microbiologist.

Here's why:

* Microbiology is the branch of biology that studies microorganisms, which are organisms too small to be seen with the naked eye.

* Microorganisms include bacteria, archaea, fungi, protozoa, and viruses.

* Microbiologists study the structure, function, growth, evolution, and ecology of these tiny life forms.

Let me know if you have any other questions!