Advances in laser physics and microwave techniques have made possible using a strong high-frequency electromagnetic field as a tool to manipulate the electronic properties of various quantum systems. Since the interaction between electrons and the strong field cannot be described as a perturbation, the system “electron + field”' should be considered as a whole. Such a bound electron-field object, which was called as “electron dressed by field”' (dressed electron), became commonly used model in modern physics. Historically, the modification of electronic properties by the dressing electromagnetic field was studied carefully in atomic and molecular systems. However, advances in nanotechnologies achieved in last decades have made possible to study the dressing-field effects in various nanostructures. The present talk is devoted to the theory of the effects.