Some of our talking about physiology & also the microscopic world made me think of a few articles I've seen recently. They're about micro-organisms, the tiny lifeforms that make up most of our 'being'.
Bacteria aren't the only symbiotic life forms within our skin...
Here is a clickable graphic, showing the various things throughout our body:
On a more disturbing note, there's evidence that micro-organisms may also be able to directly effect a more complex animal (like a human).
People gave George Lucas alot of crap for adding the 'Midi-chlorian' concept to the Star Wars universe, but I thought it was an interesting angle. The idea of trillions of tiny, living things creating energy fields that can be sensed or manipulated is an explanation that mirrors the vital necessity of these unseen organisms in the real world.
One thing I love about modern computing is the ability to visualize the reality that lies beyond our immediate senses. There've been many animations created that make processes on the cosmic & microscopic scales able to be easily understood.
This is a good video showing the life of the dreaded flu virus:
Finally, here's a remix of a Bjork song I came across while searching Google for things in this post. Leave it to her awesome craziness to write a song comparing love to a virus.