All this combining-images-into-the-same-document business can cause your Layers panel to get long and unwieldy. And as you learned back in Chapter 3, loading a document with layers can increase its file size and even slow Photoshop down (especially if you've got an older computer or very little memory). Fortunately, if the images you want to combine use the same color mode (Choosing a Color Mode), there's a solution.
Sure the Clone Stamp tool is great for tricks like banishing blemishes (Zapping Shines and Shadows) or giving someone a third eye, but it has other uses, too. To prevent your Layers panel from becoming overcrowded, use this tool to copy bits and pieces of an image from one open document to another. Using the Clone Source panel—the clone source is the object you're copying—you can clone from up to five different sources whether or not they're in the same document.
Here's how to clone from one open image into another:
Open the source (the image[s] you're cloning from) and the target (the image you're cloning to).
To choose clone sources in documents other than the current image, open the source documents. Click the Arrange Documents button in the Application Bar (Arranging Open Images) to choose a preview method that lets you see all your open documents or just click each document's tab to activate it (see Chapter 2, Guides, Grids, and Rulers, for more on working with tabbed documents).
Press S to grab the Clone Stamp tool, and then open the Clone ...