First X-ray - 1895 - Anna Bertha Roentgen's Hand

While working in his Wurzburg, Germany lab - on the 8th of November, 1895 - Wilhelm Roentgen noticed something peculiar.

Trying to determine whether cathode rays were able to pass through the glass of a Crookes tube, he saw an unexpected glow on a nearby screen. Because he didn't understand what he saw - or the nature of the rays causing the glow (on a chemically coated screen) - he called them "X-rays."

Not realizing that X-rays can be dangerous, and trying to learn more about what he had discovered, Roentgen conducted experiments in his lab. Soon he learned these strange rays could penetrate human skin, but not bones. He also realized they could be photographed.

As we learn from the Library of Congress website:

While experimenting with the Crookes tubes, Roentgen found that when he covered the tubes with a black paper and turned on the electrical current, a fluorescent substance nearby glowed. He noted that these unknown, invisible rays could pass through some substances such as flesh, but were stopped by other, such as metal or bone.

To prove his discovery, Roentgen took an X-ray of his wife's hand. This is an image of that first-ever X-ray of Bertha Roentgen's hand. It was taken on December 22, 1895.

Roentgen quickly realized the power of his discovery, but he had no desire to personally profit from it. He never sought a patent, and he freely shared his information with others.