Tiny X ray beam reveals hidden photographs from the 19th century
https://www.upi.com/Science_News/2018/06/22/Tiny-X-ray-beam-reveals-hidden-photographs-from-the-19th-century/1201529690349/?utm_source=sec&utm_campaign=sl&utm_medium=1 Source Cited: www.upi.com Sign in to see full entry.