Bose-Einstein condensed atomic gases are a new class of quantum fluids.They are produced by cooling a dilute atomic gas to nanokelvin temperatures using laser and evaporative cooling techniques.The study of these quantum gases has become an interdisciplinary field of atomic and condensed matter physics.Topics of many-body physics can now be studied with the methods of atomic physics.Many long-standing predictions of the theory of the weakly interacting Bose gas have been verified,including thermodynamic properties of the phase transition and dynamic properties such as shape oscillations and sound propagation.Stimulated light scattering was used to determine the dynamic structure factor both in the phonon and free-particle regime. Atomic Bose condensates show a variety of novel phenomena which include multi-component spinor condensates, magnetic domain formation, miscibility and immiscibility of quantum fluids, and finite-size effects.