Use a black nylon spudger to pry off the shell.

Work your way along the seam to release the tabs connecting the top and bottom of the mouse.

Do not use a metal spudger for prying, as it may damage internal components, such as the main circuit board, that are not visible.

Gently squeeze the sides of the mouse while using the spudger to pry the top case away from the bottom. The pressure will cause the mouse to open.