Loading a TreeView with a large amount of data gradually

Hello,

I am developing a C# asp.net application.
I am using a TreeView with about 4-5 levels of hierarchy which should display a very large amount of data.
When loading the Tree with all of the data I should display, the page is stuck.
Is there a way to load the TreeView gradually? Maybe 3 first levels first and onClick, add the inner levels? Or, is there another way?

Thanks