Inflation has revolutionized cosmology primarily because it has eliminated the dependence of cosmological modelling on initial conditions. Thus inflationary cosmology is able to account for the present universe starting from a wide range of initial conditions. This volume reviews the presents state of subject. Each chapter consists of a brief introduction followed by reprints of important papers. Experts in the field are also provided with a unifying view point. Contents: InflationIs Ω = 1Dark MatterFluctuationsGalaxy Formation and ClusteringThe Microwave BackgroundBaryon GenerationModelsMonopolesAppendix — Field Theory Background Readership: High energy physicists and astrophysicists. Keywords:Big Bang;Early Universe;Inflation;Galaxy Formation;Dark Matter;Cosmology;Universe Flatness;Universe Homogeniety;Monopoles;Phase Transitions;Fluctuations;Thermal Field Theory;Slow-Rollover Transition;Scale Invariant Spectrum