How to turn on the coordinates grids

when i created a new project there is nothing but a camera. That no guiding coordinates grids makes me lost and feel dizzy. so anyone know how to turn on the grids?

Check this image : http://docs.unity3d.com/Documentation/Images/manual/SceneViewNavigation-4.jpg

See the Sun Icon (toggles lights in scene view)? And next to it is a square icon (this is meant to be a picture frame with a picture of a mountain!), click on that to toggle it on/off. Note that when the ‘PictureFrame’ is disabled, the grid is visible =]