The author gives a brief historical account of the development of radiography in the past 100 years. Only one year after Mr. Röntyen had discoverd the x-ray method (1895) it was used to examine a painting by Dürer to detect fraudulent imitations. Non-destructive testing methods have since become increasingly important in various fields of conservation of cultural properties: to discover earlier painting layers, to show the inside of bronzes, the construction of musical instruments, the composition of mummies, fossils in stone and so on to meet all these tests, Röntyen rays have been modified and improved by combining them with new techniques.