CLICK HERE for a FREE copy of Population: In the Trillions from the Guide To Getting It On. This is a new chapter from the upcoming 9th edition. IMHO it is fascinating information that every woman and straight man should read.
For a great explanation of microbiomes in the human body, check out Your Microbial Friends from the University of Utah and click on different parts of the illustrations.
The image above is from the wonderful Tumblr Naked Tea!