Expandable list

We’ve all seen them but I can’t think of what to call it so I can search for it.

I’m trying to make a list that will expand to reveal a detail of that item when you click on it.

Example:

By default the menu would look like this:

MenuItem 1
MenuItem 2
MenuItem 3
MenuItem 4
MenuItem 5

But when you click MenuItem 2 then 3, 4 and 5 move down as 2 expands and you’re left with:

MenuItem 1
MenuItem 2
blah blah blah blah blah blah blah blah
blah blah blah blah blah blah blah blah
MenuItem 3
MenuItem 4
MenuItem 5

Does anyone know where I can find a tutorial or example of this so I can take it apart to see how it works?