Research towards materials and devices determined by dimensions and structural control in the nanometer range is a large effort with many resources dedicated worldwide. This interest is driven, on one hand, by basic science, because quantum phenomena determine the properties and pave the road towards new functions. On the other hand, rapid development of industrial technology demands materials and devices with more functionality, higher switching speeds, and higher integration. These requirements led to the development of fabrication techniques on the atomic scale which open the way towards the realization of revolutionary concepts in solid state science and technology.