Officers on the popular TV show CSI could soon be using a new fingerprint detection method developed at Los Alamos National Laboratory. It detects minute traces of sodium, potassium, and chlorine in salts left behind in fingerprints. The technique, called micro-X-ray fluorescence, makes the salts visible and gives the technique its name, MXRF. It has several advantages over the current method, contrast enhancement, in which prints are treated with powders, liquids or vapors to make them visible and photographable. For example, MXRF will work much better on fibrous papers, textiles, wood, leather, plastic, adhesives and human skin. It's also better for finding children's fingerprints which don't contain sebum, an oily substance that makes powder stick to adult prints.