Abstract: The magnetic behavior of lithographically defined thin film elements of permalloy imaged by Lorentz microscopy is described. Elements of thickness <100 nm, with in-plane dimensions in the micron and sub-micron range and of varying shape, have been subjected to in situ fields using an electron microscope that has been optimized for magnetic imaging. The information provided from the imaging modes has identified the details of the magnetization reversal mechanisms in the elements during the course of a hysteresis cycle. In particular, domain wall clusters which form at the edges of the elements are observed prior to switching of the magnetization. Results are described from elements with near single and multidomain structures with different geometry.