Been exploring bacteria and human microflora, or more correctly, microbiota.
Facts I did not know:
1. There are about 1000 different species of bacteria inhabiting our body, most either harmless or beneficial, unless host is immune compromised.
2. There about numerically ten times more bacteria on and in our bodies than there are cells.
3. There are many bacteria that are unculturable and only distinguishable by DNA sequencing. The culturable bacteria, "constitute <10% of the total bacterial population seen with DNA-based techniques; that is, most of the bacteria present on the human skin or in the gut are species known only by their DNA, and are species that until very recently were completely unknown to science."
Source: Wikipedia entry on Human Flora.