December 28th, 1895
Tesla had originally noticed what he described as "a very special radiation" years earlier when working his "carbon-button" lamp. He produced pictures he called "shadowgraphs" and had performed numerous experiments with them up until the fire at his lab. Upon learning of Röntgen's discovery, Tesla wrote him and sent some of the pictures recovered from the fire. Röntgen replied and asked Tesla how he produced them.
