A method for the visualization of mold filling during a thermoplastic imprint at a microscopic level was developed, which is based on superposition of images of a series of different states of imprint. The animated movie sequence gives an insight into the complex flow of polymer and shows how voids are forming and vanishing during the imprint process. It can therefore be used as a tool for optimization of processes and improvement of stamp design. (c) 2007 American Vacuum Society.