Show History Browser
Clicking on this button will open the History Browser enabling access to the available history states. The History State selector is used to select which state in the history to compare the current state to.
Once the History Browser is displayed, a list of all applied enhancements will be listed. Clicking on a state will immediately revert the image back to that state. You may then either click on another state to revert the image again, or adjust the image controls. Adjusting the image controls after reverting back to a previous state will permanently erase any subsequent steps.
Clicking and dragging the History State selector (available while in the split and side-by-side views) will set the before value for the Compare button, split view, and side-by-side view.
Dragging the History State selector to the Original Image state will allow you to compare the current black and white image to the original color image.
Shortcut (opens both the Preset Browser/History browser palette as well as the right-hand control palettes): Tab key