Microelectronics: this goes from the material to the architecture of systems, going through the process, the "device", the circuit. In recent years, we have been talking about nano-electronics, both in the industries and the public entities concerned; it is a reality, even if a passing fad and more pragmatically, the search for contracts, are well known to the use of this prefix. Each specialty gives a definition of this term; for the moment, let us say that nanoelectronics concerns electronic systems which components include at least two "clearly" sub-micronic dimensions, typically less than 100 nm. This book seeks to provide the core of modeling in micro (nano) electronics Introduces the equations underlying the modelizations and, ultimately, the related simulations Proposes what modifications should be made with respect to modeling, to effectively return on the same level to the field of nanoelectronics.