This multi-investigator, multi-disciplinary proposal is focused on magnetic and optical properties of semiconductors containing magnetic ions, so-called dilute magnetic semiconductors (DMS). Both semiconductor heterostructures and bulk crystalline material will be investigated. The program involves a unique combination of high magnetic fields, low temperatures, advanced optical techniques, and new materials development. The majority of the experiments will be conducted at the National Magnet Lab. The collaboration invloves several universities, industrial labs, both theory and experiment, as well as DMS workers in Poland. The DMS materials display a range of scientifically interesting and technologically important properties, including optical effects like large Faraday rotation and transport phenomena such as the so- called giant magnetoresistance effect. Both are of interest for possible application as information storage technologies.