Nano science and technology span a wide range of areas and might mean different things to different people. A scenario of the basic physics may be composed of two steps: (1) the properties of an isolated nanosystem and (2) its interaction with the macroscopic world. Quantum theory of the interaction of a nanosystem with a macrosystem is the object of this talk. It has implications for control, measurement, and decoherence of a single (as opposed to an ensemble of) nanosystem. This talk will illustrate these issues with a specific theoretical and experimental approach for electron excitations in one or two semiconductor dots. The contact between the nanosystem and the macroscopic world is through the electron-photon interaction. The implications for application to technology will be discussed