Unity UI How to make tooltips for button?

I want to show tooltips whenever player mouse over button.

I put a script on button with OnMouseEnter(), but not work.

 

uGUI doesn't use these old message broadcasts via Method-Name anymore AFAIK.

Instead add an EventTrigger component to your button and add Pointer Enter and Pointer Exit events to it. There you can add methods which should be called on these events.