Your hair knows where you've been

[Yang Li]

From a single strand of hair, scientists can now determine where a person has been living recently. The technique analyses heavy isotopes that vary according to local tap water, and is beginning to be used by US police to investigate unsolved cases.
通过检测头发中的重同位素可以知道你去过哪里，呵呵
http://www.rsc.org/chemistryworld/News/2008/February/26020801.asp

（J Ehleringer et al, PNAS, 2008.  DOI: 10.1073/pnas.0712228105）