New Experimental handmade Art - "Similitudes" - two artworks

In this experiment I chose two of my old friends and I drew behind them two elements without any apparent relation. It was interesting to note how these two drawings can be similar yet very different at the same time. In the first image I represented the hippocampus enlarged under a microscope. In the second picture I drew a galaxy and its branch.
I drew before only the faces of the two friends. Then I sat in front of these two portraits. I have observed them for a long time. After I chose the two elements behind them. There is a correlation between the two friends, between every man and its element, and finally between the two elements.

I drew with a very soft pencil and then I used a single oil color.
I used two smooth wood panel 80x80cm.

Work in progress
I drew before only the faces ...