How to Use the Fill with History Feature in Photoshop CS6
The Fill with History Feature in Adobe Photoshop Creative Suite 6 is useful when you want to be selective. If you can easily select the area that you want to replace with a specific state, you can use the Fill with History feature. Suppose you don’t like the sky in a particular image. You select the sky area and then add clouds by using the Clouds filter.
After you make those changes, you want to put the original sky back, but you don’t want to reverse any of the other edits you performed. Just follow these steps to replace an area by using the Fill with History feature:
Click in the far-left column of the state you want to use as the source for the Fill with History function in the History panel.
For example, select the state that has the original sky.
With your current state active, use your favorite selection tools to select the area that you want to replace.
For example, if you remembered to save your original sky selection before you added clouds, you can choose Select→Load Selection and retrieve that selection.
Choose Edit→Fill and then select History from the Use pop-up menu.
Click OK to fill the selection with the image area from the selected state.