  Currently, molecular tunnel junctions are recognized as important active
elements of various nanodevices. This gives a strong motivation to study
physical mechanisms controlling electron transport through molecules. Electron
motion through a molecular bridge is always somewhat affected by the
environment, and the interactions with the invironment could change the energy
of the traveling electron. Under certain conditions these inelastic effects may
significantly modify electron transport characteristics. In the present work we
describe inelastic and dissipative effects in the electron transport occurring
due to the molecular bridge vibrations and stochastic thermally activated ion
motions. We intentionally use simple models and computational techniques to
keep a reader focused on the physics of inelastic electron transport in
molecular tunnel junctions. We consider electron-vibron interactions and their
manifestations in the inelastic tunneling spectra, polaronic effects and
dissipative electron transport. Also, we briefly discuss long-range electron
transfer reactions in macromolecules and their relation to the electron
transport through molecular junctions.
