Sample code:
heading 1
heading 2
paragraph
You can simply implement the exact same selector:
$('#container h1')
Which selects every h1 element found within the #container element, or:
$('#container > h1')
Which selects only those h1 elements that have the #container element as their parent (not grandparent, or other form of ancestor).
Or, if you prefer:
$('#container').find('h1')
You could also restrict it to a particular h1 element:
$('#container h1:first')
Which selects only the first h1 element within the #container element.
References: