I'm sure you have heard of 'good and bad' bacteria. You wash your hands to get rid of germs, and have been doing so since elementary school. But take a moment and gaze not to the heavens, but at your own body. Your hands right now are covered with living organisms. Dive millimeters deep into your fingers and the types of microbial residents change completely. For each part of your body, there is a unique microbial ecosystem.