Many parents tend to grow increasingly frustrated when their children suddenly become question shotguns, going from one question to another, faster than the parents can dish out answers. Comedian Louis C K can at least turn these episodes into hilarious material for his stand-up. Things, of course, tend to turn particularly frustrating when the shotgun turns into a fully automatic machine gun full of 'why.' I wonder if the frustration is not really about the children but about the parents' sudden recognition of the limits of their own understanding...
In any case, if you happen to find yourself surrounded by a bunch of pre-schoolers outflanking you with their innocent inquiries, maybe you can take advantage of their curiosity and teach them a little bit not only about the things we know (or even about the things we do not yet know), but about how we might be able to start thinking about these questions, and how the very fact of our ignorance can become the platform to future discovery, as the following animation from the TED people shows