Semiconductor devices are rapidly heading towards nanometer sizes, with dielectric gate oxides already in the 2-3nm thickness range and transistor channel lengths of order 10-20nm. There is good reason to believe, therefore, that physical limits imposed by atomic level granularity will dominate operation of semiconductor devices in the future. Thus, recent work has identified a physical limit for the thickness of SiO2 in order to maintain its insulating character. [1] On the other hand, new opportunities are created, based on new behavior at the atomic level. In the presence of very high local electric fields, for instance, the local electronic structure can change from insulating to conductive, forming a very small, very fast “Mott” transistor. [2] In a single molecule having a localized electronic level which is positioned well with respect to a conducting environment, single electron transistor operation may be possible at room temperature. [3]