This tree is created collapsed
Notice that you can click on the top categories.
Collapse all -- Collapse the whole tree and only show the top branches
Expand all -- Expand the tree and show all branches.
Toggle lines -- Hide/display the lines that connect the various nodes.
Open "World" -- Open to branch that includes the "French" node
Open to "Recreation" -- Open to branch that includes the "Travel" node

When you click on a node the following will be updated.
You can of course customize the code to take actions other than displaying the node.