Change the stack order of objects
With any two objects on the artboard in Microsoft Expression Blend , one object is always higher on the stack of objects than the other object. The top of the stack is the front-most object. When you insert an object into a document or layout panel, the object is automatically placed on top of other objects in the active container object. To change the order of objects, you can use the Order commands on the Object menu or drag the objects in the objects view under Objects and Timeline in the Interaction panel.
Do one of the following:
In the Interaction panel, under Objects and Timeline, drag the objects up or down in the objects view to create the desired stack order.
Select the objects that you want to move, point to Order on the Object menu, and then click one of the following:
Bring to Front to bring the object all the way to the front of the stack.
Bring Forward to bring the object forward one step in the stack.
Send Backward to send the object back one step in the stack.
Send to Back to send the object all the way to the back of the stack.
You can also change the order of objects by using the Order commands when you right-click an object on the artboard or under Objects and Timeline.