Scientific illustrations make us able to see complicated processes that are invisible to the naked eye, because they are either too small, or other structures prevent us from seeing them.  

E.g. Immunological processes in cancer, organic processes in plants, the development of new life in a womb or egg, the anatomy of a certain species...

Another important advantage lies in the ability to focus only on the relevant information, by leaving out distracting and/or unimportant elements.

What information is absolutely necessary to show, and what is superfluous and can be left out? 

E.g.: if the focus lies on one particular organ in our body, all irrelevant other structures like fatty tissue, blood vessels etc. can be left out or made transparent, so they don’t distract from the topic of interest.

Having a clear and aesthetically appealing visual, leads to a better understanding of the illustrated  topic. 

E.g.: explaining a specific surgery to patients that don’t have medical knowledge, educational materials , …