creating child pages from navigation bar

is it possible to create child pages that show when you hover over or click any of the main navigation bar page headings? I have many pages I need to create and need them to be accessible under just a few of the main pages listed in the navigation bar.  For example:  When someone hovers over the About Us link in the navigation bar, I want several more links to "drop down" revealing pages for Company History, Board Members, and Staff Members.

Can this be done?