More about treemaps...

Looking at the background for treemaps:
"During 1990, in response to the common problem of a filled hard disk, I became obsessed with the idea of producing a compact visualization of directory tree structures."

If I understand this concept correctly, it's about deeper sets. 

It's possible that treemaps might be useful for comparing changing hierarchies. 

More useful than a pie-chart because of the hierarchial relationships. 

CD4, CD8 
Then inside CD4 and CD8

Generate a treemap for each patient - perhaps not very useful 

Generate an average treemap for normal, normal ratio and inverted ratio. 

Clearly there is a challenge reflecting the variation but we might be able to do the means. 

Or maybe not....

Interesting....