The Image Manipulation History screen lists all of the Tool and Effect actions performed on the current image.  The manipulations are shown in reverse order of occurrence, with the most recent actions listed first.  If the most recent manipulation has been Undone (indicated under the Order column), it can be flagged to reapply by pressing the Redo Undone button.  Selected items can be flagged to Undo with the Undo Selected button.  The Modify Options function can be used to alter the parameters of a selected Tool or Effect action before it is reapplied.  Press the Process History button to recreate the manipulations of the image as needed, taking into account Redo and Undo flags and any modified actions.

NOTE:  History can optionally be captured as a Recorded Sequence for use in Scripts by using the Append History to Recorded function.

Image Manipulation History Screen