This is the very first X-Ray image ever taken, by Wilhem Röntgen. He called them X-Rays because he didn’t know what the hell they were at first. So X as in “Solve for X”
It’s an image of his wife, Anna Bertha Ludwig. Because he was too much of a coward. Well, that’s not true, he had spent weeks with these things and just needed to focus on taking the image. When she saw it she said “I have seen my death” which is a little unnerving.
In 1901, Röntgen won the first ever Nobel Prize for his work into X-Rays. I wonder if he knew how much they’d change the world.