project, you're only using the Beach_umbrellas.jpg image once, so you don't need to retain the link to the file in the library. 1. With the Beach_umbrellas.jpg image still selected on the Stage, choose Modify > Bitmap > Trace Bitmap. 2. Enter the following settings: * Color Threshold: 100 * Minimum Area: 8 * Curve Fit: Normal * Corner Threshold: Normal 3. Click OK.   Adding Bitmaps to a Movie Clip Symbol Each symbol has its own Timeline. You can add layers to a symbol's Timeline just as you can to the main Timeline. As you add assets to a symbol's Timeline, they are nested within the symbol. You'll add a layer to the preview_boxes Timeline, and then add bitmap images to the preview_boxes movie clip symbol. 1. Select the Selection tool. 2. Double-click one of the green boxes on the Stage to edit the preview_boxes movie clip symbol. Flash opens the preview_boxes symbol Timeline and dims the other objects on the Stage. Double-click an instance of a symbol on the Stage to see the rest of the layout while you're editing the symbol. To see only the symbol as you edit it, double-click the symbol in the Library panel. 3. Select Layer 1 and rename it Boxes. This layer contains the green preview boxes. 4. 4 Choose Insert > Timeline > Layer. 5. Name the layer Thumbnails. You'll add the thumbnail images to this layer. 6. Drag the Vacation_1.jpg image from the Library panel to the first green preview box on the Stage. Note If the Library panel isn't visible, choose Window > Library to display it. 7. Deselect the image. Then, press Alt (Windows) or Option (Mac OS), and drag the image from the first box to the second box. The image is copied to the second box. 8. In the Property inspector, click Swap. 9. In the Swap Bitmap dialog box, select Vacation_2.jpg, and click OK. The Vacation_2.jpg file replaces the image in the second box. 10. Drag the Vacation_movie.jpg image from the Library panel onto the third box on the Stage.   Working with Buttons Use button symbols to create interactive buttons that include rollover states, which cause the buttons to change appearance when you click them, roll the mouse over them, or perform other actions. In Lesson 9, you'll use ActionScript to