The familiar pattern of dermal friction ridges can be seen across the palms of both hands and across the soles of the feet as well. However, in the case of people with certain hereditary skin diseases, these ridges do not develop. The skin stays smooth and does not leave behind any usable impression. Such disorders are extremely rare, with one of the diseases-Naegele Syndrome-only affecting one person in three million. Most people without fingerprints also have fewer sweat glands and may have other skin abnormalities as well.
A finger print is nothing more than a patch of sweat on which the dermal ridge pattern has been reproduced. Scene-of-crime experts use chemicals to make these prints visible. Every one of us has different fingerprints, which don't change over the course of our lives. Since 1901, fingerprinting has helped the police track down criminals who didn't wear gloves while committing their crimes.