The C1Menu control can hold submenus. These submenus are created when C1MenuItems are nested within the tags of other C1MenuItems. For example, placing the following XAML markup

<c1:C1MenuItem Header="First">
     <c1:C1MenuItem Header="Second">
          <c1:C1MenuItem Header="Third">
               <c1:C1MenuItem Header="Fourth">
                    <c1:C1MenuItem Header="Fifth"/>
</c1:C1MenuItem>

 between the opening and closing tags of a C1Menu would create the following:

 You can have as many nested menus as you want, although it's best not to have more than two or three submenus in a hierarchy for usability purposes.