I am reading a fascinating book by Jessica Snyder Sachs: Good Germs, Bad Germs. From page 108:

This is a great example of a positive special cause. How would you identify this? First you would have to stratify the data. It also shows that sometimes looking at the who is important (the problem is just that we far too often look at who instead of the system so at times some get the idea that it is not ok to stratify data based on who - it is just be careful because we often do that when it is not the right approach and we can get fooled by random variation into thinking there is a cause - see the red bead experiment for an example); that it is possible to stratify the data by person to good effect.

The following 20 pages in the book are littered with very interesting details many of which tie to thinking systemically and the perils of optimizing part of the system (both when considering the system to be one person and also when viewing it as society).

I have recently taken to reading more and more about viruses, bacteria, cells, microbiology etc.: it is fascinating stuff.

Related: Science Books by topic - Data Can’t Lie - Understanding Data