This is a comprehensive overview of the information yielded by electroweak probes about the nuclear-and subnuclear-scale structure of matter. Lepton-induced processes from low energy through to the highest energies are considered. The first three lectures review electromagnetic processes in hadrons; others cover the properties of partons, the behaviour of the constituents of the hadron, muon and neutrino scattering, etc. An introduction to electroweak theory including the status of precision tests and data analyses is given along with a report on the first results from HERA. The lecturers have endeavoured to achieve a balance between scientific and didactic aspects, thus making the book accessible to students of nuclear and particle physics as well as researchers.