The scientist who studies living organisms too small to see with the human eye is a microbiologist.

Here's why:

* Microbiology is the study of microscopic organisms, which includes bacteria, viruses, fungi, and protozoa.

* These organisms are too small to be seen with the naked eye and require microscopes for observation.

* Microbiologists investigate the structure, function, growth, and evolution of these organisms, as well as their impact on human health, agriculture, and the environment.