The processing window is a modified version of ImageJ's Image Window (which is responsible for displaying images). The processing window allows users to view the output of the tracker module at each step, thus providing an opportunity to fine-tune the process. The window pops up automatically when the user selects an image sequence by clicking on the set active image button of the tracker module, and it always shows the current frame series. Use the combo box in the lower felt corner of the window to select the process the output of which you want displayed.