Microorganisms that don't reside in the tissues of an individual are called free-living microorganisms.

Here's why:

* Microorganisms: This is the general term for tiny living organisms that are too small to be seen with the naked eye, like bacteria, fungi, viruses, and protozoa.

* Free-living: This means that they are not dependent on another organism for survival and live independently in their environment.

* Tissue: This refers to the collection of similar cells that perform a specific function in an organism's body.

So, free-living microorganisms are found in various environments like soil, water, air, and even on surfaces like kitchen counters. They do not rely on a host organism for survival and can exist independently.