If I had a camera," I said, "I'd take a picture of you every day. That way I'd remember how you looked every single day of your life."

"I look exactly the same."

"No, you don't. You're changing all the time. Every day a tiny bit. If I could, I'd keep a record of it all."

"If you're so smart, how did I change today?"

"You got a fraction of a...