Our what is complex but is based on units that are simple

Brain

Explanation:

The brain is the main organ of the nervous system and is responsible for the control of all the functions of our organism, even the involute actions. As you can imagine, according to the number of functions that the brain must perform, it is a complex organ, however it is divided into several simple units that allow its study and understanding to be easier to be established.

It is as if the brain is a large and complex company, difficult to be analyzed as a whole, however, this company is divided into several sectors that are simpler and easier to understand.