My Yahoo Email toolbar disappeared. How do I get it back?

When I go to the Compose a Message to do an Email, I have noticed that my "email toolbar (i.e., Spell Check / Font face / Font Size / Bold / Italic / Underline / Text Color / Highlight Color / Insert emotion icon / etc.) These ons (and the icons) have disappeared. The only way I can see them is if I run the cursor across the on face. How do I get the ons to show up again?