Jack loves to build tall towers with his building blocks. I’m convinced Jack will grow up to be an architect, an engineer, or a demolition specialist based on his experience with his blocks. Come to think of it, he could also be a crane operator.
I think he’d make a good crane operator because he’s learned how to build his towers taller than himself, and he understands the importance of balance. He understand this balance thing in this manner:
If he doesn’t have his balance as he places that last really high block, he generally falls over, and brings his entire tower down with him. It’s pretty funny to watch.
Here’s a really fuzzy action shot, right before he tumbled over one of his towers recently:

Heh, the funny thing is, when he falls while building his tower, he generally gets right back up and starts over. Like I said: Crane operator or demolition expert.