Abstract: Recent experimental and theoretical studies on the physics of semiconductor microcavities are reviewed. First, based on the Fabry-Pérot microcavity, the basic concepts and microscopic descriptions of exciton polaritons are introduced; then the potential applications of semiconductor microcavities to optical amplifiers, optical switches and single-photon sources are discussed; afterwards, the experimental realization of Bose-Einstein condensation is surveyed; finally, prospects for future developments are briefly presented.