Back in the late 1800s, detectives first started using fingerprints to identify criminals. More recently, during the past few decades, DNA has become an important tool for crime scene investigators. Now, bacteria may have their day. Hand bacteria, that is–as in the unique mix of bacteria that live on a person’s hands. The human body is teeming with bacteria. In fact, there are more bacterial cells in our bodies than human cells. Researchers have found that our hands harbor around 150 bacterial species. But the specific variety of bacteria is largely unique to each hand. Only about 13 percent of bacteria found on a given hand is shared with any other hand.