Operads and -spaces -- Operads and monads -- A? and E? operads -- The little cubes operads -- Iterated loop spaces and the -- The approximation theorem -- Cofibrations and quasi-fibrations -- The smash and composition products -- A categorical construction -- Monoidal categories -- Geometric realization of simplicial spaces -- Geometric realization and S*, C*, and ?* -- The recognition principle and A? spaces -- E? spaces and infinite loop sequences -- Remarks concerning the recognition principle