Look closely at ,your hands-are they clean? It doesn't matter how many times you was  your hands. They're still crowded with microbes, which are also called "germs" or "bacteria". Microbes are everywhere. But don't worry-most microbes don't harm you. and many actually help you stay alive. Now,  scientists say the microbes that live on our hands could be used in a surprising way: fighting crime. When police visit the scene of a crime, they often look for fingerprints to try to identifythe criminal.  But according to a recent study, investigators could even use microbes to help break a criminal case. Every person has his or her own set of microbes that live on their hands, according to scientists at,the University of:Colorado. That means the mix of different kinds of microbes on everybody's hand is unique-much like one's fingerprint. The scientists wanted to know whether this microbe mix could be used as a new kind of fingerprint-especially in a crime scene where fingerprints might be hard to find.  And policemen use forensics such as studying fingerprints to identify the criminal. "Microbe fingerprints are harder to hide," said Noah Fierer, one of the scientists. "You can't sterilize(......) a surface just by wiping it off. " His team compared the bacteria on the hands of 273 people with the bacteria found on each person's computer keyboard. For the study, the keyboards had been used only by the people who were being tested. The study showed that the mix of microbes from each per- son's hands matched the mix of microbes on that person's keyboard. The scientists were easily able to tell the 273 people apart-just by looking at their keyboards. But there are a lot more than 273 criminals. Other scientists wonder whetherthe microbe fingerprint can really be that useful. Fierer agrees that scientists have a lot more work to do before the microbe fingerprint will be a useful tool. The main idea of the passage is about  _  .
the importance of fingerprints how to clean our hands the usefulness of microbes different germs on our hands