xkcd post number 688 shows charts of the proportion of black ink in the charts in xkcd post number 688, and it has in the chart on the right a plans of the locations of the charts in xkcd post number 688, which  has in the chart on the right a plans of the locations of the charts in xkcd post number 688, and so on …

Self description (click to visit xkcd)

And for the benefit of those without infinite resolution monitors:

Pie charts all the way down (click for full size)

 Resources for those who don’t get xkcd:

http://xkcdexplained.com/

and

http://xkcdexplainedexplained.com/

and

http://xkcdexplainedexplainedexplained.tumblr.com/

and so on …