Radiography started in 1895 with the discovery of X-rays (later also called Röntgen rays after the man who first described their properties in detail), a type of electromagnetic radiation. Soon after the discovery of X-rays, radioactivity was discovered.
The practice of radiography began in 1895 with the revelation of X-rays, later named Röntgen rays after the scientist who first detailed their characteristics.  Radioactivity was soon afterward found.