Improvements in the properties of nanoscale devices based oil giant magnetoresistance or tunnel magnetoresistance depend on the capabilities of researchers to design.. fabricate, and test such devices. Optimization of these capabilities is intimately tied to the feedback provided by the quality and quantity of available microscopic characterization. The current work presents examples of the use of atom probe tomography in order to obtain microstructural characterization for a variety of nanomagnetic thin film devices including multilayers, spin valves and tunnel barriers. (c) 2005 Elsevier B.V. All rights reserved.