If you feed them they grow.
Heck, I take Caitlin grocery shopping in order to exploit her height and her brite strength.
(there's probably a law against that now)
And now I have Invader Zim in my head saying, "Explain this.. 'growing' thing to me again.."
*chuckle*
I've had the missus and my mom both ask me to grab stuff they cannot reach.