Stacks are another useful way to organize your images. Imagine a traditional light table (if you can!) and remember how you could set one slide on top of another, creating a relational stack. Well, that's pretty much what you do with Lightroom stacks.
Start in the Grid view by selecting a group of related images that you want to stack together. The images must be stored in the same folder and you can't stack from within a collection. (To select multiple sequential images, click on a thumbnail, then hold the Shift key and click on the last thumbnail in the sequence. All the thumbnails between will also be selected.) Figure 3-95
Next, right-click on one of the selected thumbnails. Be sure to click on the image area, not the outer frame. As long as the selected images are stored in the same folder, this should bring up the contextual menu shown here. Figure 3-96 You can get the same options by selecting Photo→Stacking from the menu bar.
Your selected images will be collapsed into one and the visible image will display a number in the upper left corner indicating the number of stacked images (circled). Figure 3-97 You can change the order of an image in a stack via the Stacking menu or the following keyboard ...