Radio Astronomy -- Principles of Synchrotron Emission in an Astrophysical Context -- Non-Thermal Emission from Extragalactic Radio Sources: A High Resolution - Broad Band Approach -- The Observational Properties of Blazars; Selection, Relationships and Unification -- Observing Blazars with VLBI -- Theory of Relativistic Jets: Basic Concepts -- Parsec-Scale Morphologies and Properties of Radio Sources -- Supermassive Black Holes in the Universe -- Young Powerful Radio Sources and their Evolution -- AGN Unification; Past Present and Future -- Radio Polarimetry -- Gravitational Lensing with a Radio Bias -- VLBI Observations of Gravitational Lenses -- Scintillation in Extragalactic Radio Sources -- Supernovae -- Astrophysical Masers -- Radio and Optical Interferometry -- Optical Interferometry: Astronomical Application -- Data Analysis -- Deep Fields: The Faint Sub-mJy and MicroJy Radio Sky -- Space VLBI -- VLBI for Geodesy and Geodynamics -- Tropospheric and Ionospheric Phase Calibration -- Ground Based VLBI Facilities - the European and Global VLBI Network.A masterly survey of the last 13 years of Very Long Baseline Interferometry, reviewed in light of the most advanced astronomical observations. Topics covered include: Nonthermal emission from extragalactic radio sources; Principles of synchrotron emission in relation to astrophysics; Theory of relativistic jets; Young, powerful radio sources and their evolution; Scintillation in extragalactic radio sources; Radio and optical interferometry; Radio polarimetry; Unified schemes; Deep fields; Tropospheric and ionospheric phase calibration; Supernovae; VLBI for geodesy and geodynamics.