the discovery of x-rays came from experimenting with crookes tubes, an early experimental electrical discharge tube invented by english physicist william crookes around 1869-1875. in 1895, wilhelm röntgen discovered x-rays emanating from crookes tubes and the many uses for x-rays were immediately apparent. one of the first x-ray photographs was made of the hand of röntgen's wife. the image displayed both her wedding ring and bones. on january 18, 1896 an "x-ray machine" was formally displayed by henry louis smith. a fully functioning unit was introduced to the public at the 1904 world's fair by clarence dally.