"CHIPS: Solid-state terahertz emitter devised"

A unique, inexpensive solid-state source of terahertz radiation has been demonstrated by Argonne National Laboratories, working with researchers in Japan and Turkey. Terahertz (THz) frequencies can penetrate clothing, leather, fabric, cardboard, paper and some building materials, but not metal or water. Since they are non-ionizing (unlike x-rays, which can knock your electrons out of orbit, terahertz emitters enable "x-ray vision" applications without the health hazards, for everything from security scans to medical and dental imaging.
Text: http://www.eetimes.com/showArticle.jhtml?articleID=204203898