You have removed the aluminum shell that was glued onto the bottom of Apple's Magic Mouse.

What you have left with are the upper and lower halves of the mouse. They are held together by four tiny black plastic posts on the bottom half, that are inserted into plastic loops on the top half. WARNING: Proceed with caution. If you break any of these black plastic posts or loops, it might be game over.

The two halves are connected by a wide ribbon cable that is somewhat fragile. WARNING: If you tear this cable it is game over for this mouse.

Proceeding with caution, take a small pry tool and pry one of the plastic loops off of its black plastic post. Pry the loop in the outboard direction while applying gentle pressure separating the upper and lower halves of the mouse. The loop should pop off the black plastic post.

Continue to release each of the remaining three black plastic posts. Remember that on the Apple logo end of the mouse there is a fragile ribbon cable that you dare not tear.

Once you release the black plastic posts, the only thing holding the mouse together is a very fragile ribbon cable [see second photo]. WARNING: You don't want to tear the cable or pull it out of its socket (because it is tricky to put it back into the socket). Proceed with care!