A highly scientific article about mitochondria
After reading some posts from 
Mitochondria are very interesting. A main topic of the Wahls Protocol - a diet for combatting Multiple Scelerosis. They are at the basis of our energy and are antique at the same time
The inner mitochondrial membrane contains the metabolic machinery for aerobic metabolism, an evolutionary adaptation to oxygen-rich environments, which coincided with the endosymbiosis, or engulfment, of the ancient autotrophic bacteria that were the predecessors of these eukaryotic organelles.
In other words, a long long time ago, some bacteria and cells shook hands and became one.
The rest is difficult to read but if you have some background there'll be sure a few "Aha's"! Might be highly appreciated by @candadian-coconut?
source: http://www.greenmedinfo.com/blog/reverse-cancer-targeted-mitochondrial-restoration