Are ViewControllers in Mainwindow.xib always loaded by default on launch ?

Question

I am new to Iphone development and try to grasp the idea of ViewControllers.

I have a XIB file MainWindow.xib... inside I have a viewcontroller and a view.

I see that everytime my app launches, the ViewDidLoad gets called (I have NSLog Statements that fire in that function).

What if I want to delay load that view controller in the XIB ?