The identification of the occurrence of a material which has a structure that is ordered but not periodic in an electron diffraction work triggered a sensational discovery in 1984. It was found that a rapidly solidified alloy of Al with 10–14% Mn possesses an icosahedral symmetry in combination with long-range order. The discovery of such aperiodic forms has resulted in rewriting the basics of crystallography and has paved the way to search for these materials in Nature and look for specific applications.