Beware of giving a lock of hair as a keepsake -- it could end up at Psychemedics, which provides drug testing services through the analysis of hair samples. Its tests, which it markets under the brand name RIAH (or Radioimmunoassay of Hair), not only reveal that a substance has been consumed, but also detect patterns of use over time; the tests look for cocaine, marijuana, PCP, Ecstasy, and opiates. The company's primary market is employers, who use the service for pre-employment screening, as well as random testing of current employees. Psychemedics also sells its service to hundreds of schools nationwide (and in some foreign countries) and offers a service to parents worried that their kids might be on drugs.